Nokia is in a bind. The company announced more than a year ago that it planned to abandon both Symbian and MeeGo in favor of Windows Phone, the emerging mobile Microsoft platform that is currently still emerging more than two years after it was introduced as “Windows Phone 7 Series” in February 2010. Nokia and Microsoft had a lot in common, of course. Beyond an executive who ran Microsoft’s business division before joining Nokia as its CEO, both companies were once giants in the smartphone space. Microsoft had long since toppled, and Nokia’s market share was plummeting as its products continued to struggle against Android and the iPhone. Just two smartphones have emerged so far from Nokia and Microsoft’s deal since it was announced more than a year ago, and only one launched with carrier support in the United States. Now, Nokia is preparing to release its first flagship Windows Phone for the U.S. market — the Lumia 900 — and I spent the past week testing the handset in order to determine whether or not this might finally be the device that puts both Nokia and Microsoft back on the map.

The Inside

In a world where smartphones are judged on paper long before they find their way to consumers’ hands, the Lumia 900 is a tough pony to bet on.

Several smartphones with quad-core processors will launch in the coming months and the Lumia 900 has a single-core 1.4GHz Qualcomm Snapdragon CPU. We already have phones with giant qHD and 720p HD displays on the market — Samsung is even prepping its first smartphone with a 1080p HD display according to BGR’s sources — and the Lumia 900 has a 4.3-inch ClearBlack AMOLED display with 480 x 800-pixel resolution. Apple’s iPhone 4S includes as much as 64GB of internal memory and numerous Android handsets come with 32GB of internal storage expandable to 64GB thanks to microSDHC support, but the Lumia 900 comes with 16GB and no memory card slot.

Nokia itself doesn’t quite know how to position its new flagship smartphone on paper. Case in point: “Bing,” Internet Explorer 9″ and “HTML5” are three of the first six items Nokia lists at the top of the Lumia 900’s specs page.

Lucky for Nokia, this “world” of specs and paper champions is a relatively small one that is generally confined to gadget reviewers, tech bloggers and smartphone enthusiasts. While the spec-head mentality sometimes trickles out into the mass market, consumers by and large don’t care about the technology that powers their gadgets. Even if they toss out the term “dual-core,” they typically have no idea why a dual-core chipset may or may not be better than a single-core processor. Instead, they simply want their gadgets to perform well.

The Lumia 900 is a remarkably smooth smartphone, thanks in no small part to Microsoft’s mobile platform. The user is greeted on the home screen by two columns of brightly colored tiles that make up the most recognizable part of Microsoft’s “Metro” user interface. Each tile represents a different application, for the most part, and tiles configured to do so can display live information such as unread message counts, current weather conditions or top headlines. A swipe to the left reveals the full list of apps installed on the phone, and those are the only two screens on the device that aren’t inside an app.

Of course bad apps are bad apps regardless of a device’s platform or specs, and some third-party apps I tested had a very difficult time running on the Lumia 900. Interestingly, I find that the worst offenders among my regularly used apps — that is, the apps I use that have trouble running on every Windows Phone I’ve tested — seem to have even more trouble on the Lumia 900 than they do on other devices. So, where an app might take occasionally get stuck refreshing a screen for a second or two on the HTC Titan, that same app might get stuck for three seconds on the Lumia 900.

Nokia’s new smartphone also features 16GB of internal memory that is not expandable, and 512MB of RAM. Local connectivity options include Wi-Fi, USB 2.0 and Bluetooth 2.1 + EDR, and the Lumia 900 features compatibility with 10 different cellular bands — GSM 850/900/1800/1900, WCDMA 850/900/1900 and LTE 700/1700/2100.

This will be the first Windows Phone to launch in the U.S. with 4G LTE support and while AT&T’s LTE network is still quite young, users with coverage will notice the speed boost immediately; during my tests, I saw download speeds that averaged more than 15Mbps and upload speeds in excess of 5Mbps. Unlike Verizon and Sprint, however, AT&T subscribers also have a speedy previous-generation network to fall back on. I experienced download speeds in excess of 6Mbps on the Lumia 900 in and around New York City on AT&T’s HSPA network, while Verizon and Sprint’s 3G networks typically deliver download speeds in the 1Mbps to 1.5Mbps range in my region.

An 1,830 mAh battery powers the device and while it certainly doesn’t last as long on a single charge as some other modern handsets, I found that the Lumia 900 could easily power through a full day of moderate usage that consisted of sending and receiving dozens of emails, taking a few phone calls, various sporadic app usage, snapping a number of photos and uploading them to Dropbox, streaming some music using a third-party Pandora app and more. Wi-Fi seemed to have a big negative impact on battery life, and streaming video for even 20 minutes over Wi-Fi one morning made it difficult for the battery to make it all the way to the end of my work day.

As is common among Nokia smartphones, I found reception on the Lumia 900 to be very solid. The fact that the phone includes an “LTE” indicator for 4G LTE signal and a “4G” indicator for HSPA signal is horribly confusing and more than a little disturbing, but I found that the Lumia 900 consistently showed more bars than other AT&T smartphones in the same room. Voice calls were loud and clear on the ear speaker, the quality of the speakerphone was above average, and I didn’t drop a single call during a week of testing the device.

The Outside

Full-touch smartphones are a dime a dozen right now, and to say smartphone designs are beginning to blend together is putting it mildly. Nokia’s Lumia 900, however, does not blend.

Even without the phone’s unique color choices, the Lumia 900 features a fantastic design that is unlike any other smartphone. Aside from the Lumia 800. And the N9. Nokia’s manufacturing process transforms a single piece of polycorbonate into a stunning unibody smartphone case, and the result may be one of my favorite smartphone designs in recent history. The Lumia 900 is gorgeous.

A large panel of Gorilla Glass covers the phone’s 4.3-inch AMOLED ClearBlack display along with a front-facing camera and Windows Phone’s three mandatory hardware buttons, taking up most of the Lumia 900’s face. The display, I should note, is very competitive with leading smartphones — color are vivid and I found visibility in sunlight to be much better than on a number of rival phones with AMOLED displays.

The bottom of the handset is home to a microphone and loudspeaker, while the top of the device includes a standard 3.5-millimeter audio port, a secondary microphone for noise cancellation, a microUSB port and a microSIM slot.

The smooth, curved right edge of the Lumia 900 includes plastic volume rocker, power and camera buttons, and the left side is completely bare. The back of the phone is home to a dual-LED flash and a small chrome insert featuring Carl Zeiss and Tessar branding along with the rear camera lens. Overall, the smartphone is 5.03 x 2.7 x 0.45 inches in size and it weighs a hefty 5.6 ounces. It does feel a bit large and heavy in the hand, but it’s no larger than other phones with similar display sizes and I like the weight — it makes the phone feel substantial.

The clean lines on this remarkable design are largely uninterrupted, and it really pops in cyan and white, though the white version of the Lumia 900 will not be available until later this month. In black, the smartphone is much more understated but still a sight to behold. And it’s not just the overall look of the phone that separates it from the pack, it’s the minor details as well. Things like the tapering of the ends of the curved case that lead to the perfectly flat top and bottom, or the 1-millimeter raised glass edge that surrounds the display add unique touches that come together to further separate this smartphone from the pack.

The Upside

The overall user experience offered by the Nokia Lumia 900 is fantastic. This stems from Microsoft’s mobile platform which, despite being praised regularly by gadget reviewers, has failed to gain widespread adoption. Despite Microsoft’s muscle and support from several big-name vendors such as Samsung and HTC, Windows Phone has been ignored by end-users for the most part.

In the United States, industry watchers tend to place a good deal of blame on carriers for Windows Phone’s slow adoption — Android and iOS are currently the darlings of U.S. carriers, and little effort is made on the part of sales associates to push devices running Microsoft’s Windows Phone OS to end-users. While it is true that Android devices and Apple’s iPhone are pushed much harder than other platforms, we’ll soon find out what kind of impact real carrier support will have on Windows Phone sales.

Windows Phones are incredibly responsive in most cases, and Nokia’s Lumia 900 is no exception. The interface on this phone is glued to the user’s finger during operation, and scrolling is nice and smooth. Animations are fluid and like other Windows Phones, multitasking is a breeze on this device. A one-second tap on the capacitive back button brings up the task switcher, which automatically displays the user’s most recently-used apps. This makes flipping back and forth between the email composition screen and a web page, for example, an absolute breeze.

There are still a number of apps that aren’t compatible with the “tombstoning” feature introduced with Windows Phone 7.5 Mango, however, and waiting for those apps to start up again after having switched back from another app is a hassle. Tombstoning is simply Microsoft’s terminology for the process that pauses an app when it is sent to the background and allows it to restart from its paused state when the user opens it again.

Another one of my favorite Windows Phone features, and therefore Lumia 900 features, is the implementation of “live tiles.” A quick glance at Windows Phone’s home screen reveals that the OS makes use of a terrific variation on the concept of app icons. While Windows Phone uses a grid of images to represent applications on a device just like any other OS, Microsoft’s platform transforms these icons from static graphics to living entities that exist somewhere between icons and widgets.

Live tiles can display a wide variety of information immediately as it becomes available, and the live tile system’s utility is limited only by developers’ creativity. Messaging apps can display unread message counts. Weather apps can display forecasts and snow alerts, news apps can display headlines and sports apps can display scores. Some live tiles can also utilize basic animation, so Microsoft’s Pictures tile is an ongoing slide show and the People tile flips through images of a user’s contacts.

As has likely been made clear, I am also a huge fan of the Lumia 900’s design. The hardware has a terrific weight and the shape is outstanding, with well-placed curves that manage to look fantastic and fit perfectly in the hand.

The unit I reviewed is cyan, and I have yet to come across a person who had something bad to say about the color. It catches the eye immediately and yet still manages to maintain a level of sophistication that pink phones and other crazy colors quickly lose. It does attract a fair amount of attention, though — people were constantly checking out the Lumia 900 any time I pulled it out in public — so users who don’t want the added attention may want to stick with black.

The Downside

Considering Nokia’s pedigree, I was absolutely shocked the first time I used the camera on the Lumia 900. To put it plainly, as good as the hardware design is on the Lumia 900 is as bad as I found the camera to be.

In a world that was once dominated by Nokia, the Finnish vendor’s competitors have made huge strides in recent years with regard to camera phones. Apple’s iPhone features one of the most impressive smartphone cameras on the market, and HTC just set the bar several steps higher with the cameras on its new One-series smartphones. These cameras, which are driven by a dedicated microprocessor, are capable of capturing a RAW 5- or 8-megapixel image, converting it to JPG, saving it, and returning to a ready state in 0.7 seconds.

Meanwhile, I found that the Lumia 900’s camera takes very poor images compared to these market leaders. Colors were washed out and didn’t pop at all like they do on the iPhone. The edges of objects were extremely blurry rather than sharp and clear like they are on the HTC One S I have been testing.

I also had a great deal of trouble focusing on objects at close range. Even when I tapped on an item to focus on it and snap a picture, the phone still focused on something in the background instead. Macro mode did nothing to resolve the issue.

I’m hoping some of these issues will be fixed in upcoming software updates. Considering the quality of images taken using other Nokia handsets, I have to imagine these are not problems with the optics or other camera hardware Nokia used in the Lumia 900.

Outside of the camera, apps are one of this phone’s biggest barriers. This is hardly a new issue, and it is certainly not one that only impacts the Lumia 900 or even just Windows Phone. Mobile developers, for the most part, focus their attention on iOS and Android for obvious reasons.

Nokia and Microsoft have not been shy in recognizing this issue, and the companies are both throwing money at it. Also, I think we’ll see some interesting integration with both Xbox and Windows 8 in future versions of Windows Phone that will make the mobile platform even more attractive to developers. If they can continue to woo big-name developers — and maybe even get a few exciting exclusive titles on the platform — it should help draw more attention and ensure Windows Phone can remain competitive. In the meantime, users looking for popular titles like Words With Friends, Draw Something, Temple Run and Instagram will have to look elsewhere.

Selling users on a platform where they’ll have to ditch several of their favorite apps will never be an easy task, regardless of how much incentive AT&T sales representatives are given and regardless of how gorgeous a device might be.

Beyond those major qualms, my remaining issues with this handset are relatively minor. The phone’s oleophobic coating, for example, is not on par with many rival devices. All touchscreen phones gather oils from the hand, but Nokia’s Lumia 900 seems to gather more grease than other phones. This handset also seems to hold onto oil a bit more than other devices, and I found a mobile cloth worked much better than a t-shirt to clean the display. Also, it would be nice to see this flagship phone ship with a pair of earbuds like most comparable devices do.

The Bottom Line

If the Lumia 900 fails to gain traction in the U.S. market, it will pose a huge problem for Nokia and for Microsoft. It won’t signal the immediate end for either company in America, of course, but will leave both companies in a very difficult spot.

Nokia’s Lumia 900 on AT&T is the total package in every sense of the term. It is a phone with gorgeous hardware that manages to be both classic and unique. It will launch alongside a massive marketing and advertising effort. AT&T’s retail staff is being given Lumia 900 handsets and extensive training, and the device will have prime positioning in the carrier’s stores. And on top of everything else, this flagship 4G smartphone is just $99.99 or even less on contract.

This is Windows Phone’s shot.

If the Lumia 900 cannot succeed in the U.S. under these conditions, it begs the obvious question: what else can be done? The biggest barrier, beyond the established positions and momentum currently enjoyed by iOS and Android, is likely apps.

The absence of popular apps certainly won’t be a deal breaker for everyone, however, and as someone who regularly uses all mobile platforms, I have personally been able to fill most gaps on Windows Phone with somewhat comparable apps. WhatsApp is a perfectly suitable alternative to iMessage and BBM, for example, and while there is no official Pandora app for Windows Phone, there are several third-party options such as MetroRadio. GoVoice fills in for an official Google Voice app on my Windows Phones, and there are plenty of high-quality mobile games to replace missing titles that are popular on Android and iOS.

Windows Phone is smart, fast, responsive and very well-designed, though its UI tends to be polarizing. Most people I have come across offer praise for the Metro UI in general, though some suggest that they miss a more graphics-heavy interface. I enjoy the Metro UI a great deal, though I find that there are some apps that would be better off with a more traditional interface. From what I understand, the next major version of Microsoft’s Windows Phone platform will offer a host of new options to developers that should bring immediate improvements to the quality and variety of apps on the platform.

Nokia’s Lumia 900 is a terrific smartphone that gives Windows Phone its best shot yet to succeed. The hardware is well-designed and unique, the software is intelligent and smooth, the price is right, and the 4G data speeds along with excellent reception and call quality seal the deal. AT&T’s new flagship phone is not without its faults, of course, but this handset can most certainly go head to head with the best devices on the market when it launches on April 8th.