Microsoft’s Windows Phone platform is in a peculiar place right now. Those who use the year-old mobile operating system typically offer glowing accounts of their experiences, but adoption has been anything but brisk. Carriers aren’t pushing Windows Phones with any effort worth noting — in fact, retail staffers at U.S. carrier shops have been known to steer customers away from the platform according to various reports — and in the second quarter of 2011, Microsoft’s share of the mobile market may have hit an all-time low. Microsoft’s deal with Nokia finally bore fruit this week however, and the second wave of Windows Phones has begun trickling out into the market. Among the Windows Phone 7.5 “Mango” devices that have been announced to date, one in particular stands taller than the rest, both literally and figuratively. In this review, we take a look at the AT&T-bound HTC Titan to see if this phone is worthy of its titanic moniker.

The Inside

Ever since Microsoft first took the wraps off its next-generation mobile platform “Windows Phone Series 7” in early 2010, I’ve been intrigued. Like webOS, Microsoft’s operating system appeared to offer a fresh take on the smartphone user experience. When handsets finally started shipping ahead of the holidays last year, Windows Phone delivered. It was fresh, it was unique and it was a pleasure to use. Unfortunately for Microsoft and its partners, however, consumers didn’t seem to care.

Windows Phone was truly a pleasure to use, but it was also quite clearly rushed. I can’t really blame Microsoft for rushing its new mobile platform out the door, of course, as Windows Mobile had effectively been dead for some time already. Android and iOS were crushing the market and Microsoft needed something to lure its vendor partners away from Android. And so Windows Phone 7 was born, but almost immediately dropped off at the orphanage. Vendors didn’t bother promoting the devices, carriers didn’t bother promoting the devices… even Microsoft fell oddly silent as its new platform was cast aside.

Enter Windows Phone 7.5, code-named “Mango” after a fruit so sweet when it’s ripe, it is almost impossible to resist. This was to be the company’s opportunity to regroup and deliver a series of blistering fastballs after a bases-loaded balk saw its opponents’ lead grow wider. All eyes were on London this week as Nokia unveiled its first two Windows Phones, but HTC’s Titan is already upon us, carrying Microsoft’s latest mobile OS on what is likely the largest display it will ever see.

The HTC Titan is a beast. Its 4.7-inch display gives Windows Phone a canvas that is nearly tablet-like, and the 1.5GHz Snapdragon processor driving the device makes one of the world’s smoothest operating system even smoother. In the two weeks I have been carrying the Titan, I have yet to see a crash, bogging, lag, or anything else of the sort. I can’t even say that about iOS.

Animations flutter about on the Titan, and native apps open into a usable state in the blink of an eye. The user interface is unbelievably smooth, and the UI “sticks” to one’s finger during navigation just as well as iOS. Scrolling in apps is also lag-free, though inertia scrolling is still a bit off. When the user releases a finger following a flick, the scroll seems to accelerate at the same rate regardless of how hard the user flicks. It’s awkward but hardly a major problem.

My biggest performance-related issue is the amount of time it takes most apps to refresh with new data. On AT&T’s HSPA network, data speeds are fast and latency is quite low. I regularly saw download speeds of between 2Mbps and 4Mbps during my tests in and around New York City, and upload speeds hovered between 1Mbps and 1.5Mbps while connected to HSPA. Even still, it can take 5, 6 or even 10 seconds or more for an app to refresh with even the smallest amount of new data. I haven’t quite pinpointed the culprit yet — different developers tell me different things, though everyone I’ve spoken with recognizes the issue — but I suspect that it’s often a combination of the OS and developers’ inexperience with coding apps for it.

Beyond that, I can’t stress enough how much I’m enjoying Mango. The “tombstoning” feature akin to application state-saving in iOS is implemented quite well, and apps that take advantage of it load from the background almost instantly. Enhanced multitasking features in the next major Windows Phone release will bring even more capabilities to developers and users alike, but the current solution is fast and elegant.

The Outside

The Titan is huge. There’s no reason to beat around the bush.

Supersized smartphones are becoming more popular each month — probably due in large part to the fact that vendors are flooding the market — and there are definitely advantages and disadvantages to carrying a phone this massive.

At 5.18-inches tall by 2.78-inches wide by 0.39-inches thick, the Titan is even bigger than the Samsung Galaxy S II. At 160 grams, it’s also more than 20 grams heavier. I like a heavy phone, and the Titan’s solid build and high-quality materials are more than worth the added heft to me. The majority of the smartphone’s case is comprised of beautiful brushed aluminum, save for a small rubber-feel area near the top of the rear case and a larger one at the bottom where the antenna sits.

Across the top of the phone sits a power/lock/unlock button, a small hole for the noise-canceling mic and a 3.5-millimeter audio jack. The right edge of the device is home to a slim two-stage camera button that sits beneath an equally slim volume rocker, and the left edge sports a lone micro-USB port. The bottom houses only the phone’s main microphone and a battery door release button.

On the rear of the device is a sizable camera lens flanked by a dual-LED flash and a speaker. I’ll discuss the camera more extensively a bit later. The face of the phone is made up almost entirely of smooth, oil-resistant glass. Three customary capacitive Windows Phones buttons sit across the bottom, and a front-facing camera is positioned near the top below the phone’s ear speaker. Voice calling is quite clear on the Titan, and the speaker gets loud enough to be used comfortably in noisy environments.

One thing that should not be overlooked about the exterior of the Titan is the design. Like the Sensation, HTC’s Titan features a unique unibody design that has the rear case of the device wrap around the side and top. The “guts” of the phone then sit inside the case, creating a design that positions all seams directly around the display. The result is not only gorgeous, it also means there are no uncomfortable seams to be felt by the user’s hands.

The Upside

As a complete package, the Titan is easily one of my favorite Windows Phone to date. The build is phenomenal and the Windows Phone 7.5 operating system is like greased lightning. I’m also a huge fan of live tiles.

Microsoft’s home screen UI, for those unfamiliar with Windows Phone, is tile-based. It is comprised of a grid of square and rectangular tiles that cascade endlessly. The result is a tidy home base that provides a welcome alternative to static icons. These tiles, if enabled, provide the user with information dynamically and can be updated frequently.

For example, my favorite simple weather app WeatherLive displays the current temperature, the temperature range for the day, and a graphical representation of the current weather conditions. When it rains, I see a storm cloud and rain drops. When it’s sunny, a big sharp sun covers the bulk of the tile. Another example is my favorite Google Reader-compatible RSS Reader, Wonder Reader. When enabled, the app periodically flashes headlines across the tile to let me know I have new articles waiting to be read. Messaging apps display unread counts, the Photo Hub cycles through images stored on the device, my Xbox Live avatar dances around the Games tile, and so on.

Beyond the tiles, there are a few other new features in Mango that I really enjoy. First and foremost, tombstoning and basic multitasking support are implemented quite well. Enabled apps close in a frozen state and holding down the back button for a second quickly brings up the task switcher UI. Transition animations are subtle but appreciated, and jumping between apps is lightning fast.

I also like that Mango brings Wi-Fi tethering to Windows Phones. The Internet Sharing service on the Titan is buried in the system settings in Windows Phone rather than being granted a dedicated app that I might be able to pin to the home screen, but I still appreciated having one less device to carry while testing the Titan. Wi-Fi tethering is available on a number of smartphones these days, but I typically find it unusable due to the inevitable battery drain. The Titan’s 1,600 mAh battery held up nicely even after about 30 minutes of Internet Sharing, however, and Mango includes a nifty feature: if no devices connect to the phone after a few minutes, tethering is automatically turned off. Also, if you’re tethered and then you disconnect all devices from the phone, Internet Sharing will automatically turn off after a few idle minutes. It’s one less thing to worry about.

The camera on the Titan shocked me. This has traditionally been a very weak point for HTC phones — very, very weak — but the 8-megapixel camera on the Titan captures terrific still images. The color and clarity in photos taken by the Titan is on par with the likes of Zeiss-equipped Nokia handsets and the iPhone 4S, and future Titan owners can certainly plan to ditch their point-and-shoot cameras. It also captures high-quality 720p HD video content, though the lack of an HDMI-out port or even an adapter is something of a disappointment.

Finally, Windows Phone still provides what, in my opinion, is the hands-down best email experience on any mobile platform. The UI in the email app is gorgeous and lightning fast, and it’s simple to drill down to unread items, urgent items or flagged items with a quick flick. On the Titan, the humongous display only makes things better. Productivity is the same story. Microsoft’s mobile Office suite is a joy to use for creating and editing Word documents or Excel spreadsheets, and the SkyDrive integration provides easy access to remote files to ensure that the same documents are available on your phone and your computer.

The Downside

Again, the Titan is huge. While I have gotten somewhat used to the mammoth device over the course of the past two weeks, it’s still just too big for me.

Consumers love giant smartphones. Vendors keep cranking them out and people keep buying them. While there are numerous and obvious advantages to big smartphone displays, there are also several drawbacks and the negative outweighs the positive for me.

On the one hand, the huge screen affords a great canvas for emails, web pages, images and video. On the other hand, stretching 480 x 800-pixel resolution over a panel that measures 4.7-inches diagonally means clarity and sharpness suffer. Usability suffers as well, and a perfect example is the back button. On Windows Phone devices, the back button is extremely important. There is often no way to navigate back one screen from within the UI, and holding down the capacitive back key also brings up the application switcher. While holding the device in my right hand, however, I cannot reach the back button at all. Not even close.

I also can’t reach the lock/unlock button without repositioning the device in my hand, though this is infinitely less important than the back key. This button is crucial to the operation of the device, and one-handed use is often my preferred method of operation. It just doesn’t work. Samsung solved the problem by repositioning the back button on its giant Galaxy S II smartphone to make it accessible during one-handed use. This of course left the menu key just out of reach, but better that than the back button.

Somewhere around 4-inches lies the sweet spot for me, and a scaled down device like the Titan with a display around that size would likely be my ideal Windows Phone.

My only other serious complaint about the Titan applies to Windows Phone in general rather than to this particular smartphone, and that is the third-party app situation. It’s improving every day, and Nokia’s arrival on the scene will only help accelerate developer adoption. Today, however, things are not where they need to be.

I cannot for the life of me find a decent Twitter app, for example. There are a handful of usable options — I’ve landed on Seesmic for the time being — but they’re all slow and clunky. This goes back to my earlier note that data calls take entirely too long. Microsoft needs to fix this problem because it can be quite off-putting, especially in areas with sparse cellular coverage. The Metro interface is beautiful, but it loses its allure quickly when a data refresh takes 10 seconds.

Today, Windows Phone is often an afterthought for developers and the selection in the Windows Marketplace reflects that. This will change, and Mango introduced new APIs and capabilities that afford developers more flexibility. Right now however, there are many go-to apps that I simply can’t find in the Marketplace, and I suspect many users coming from more established platforms will make the same claim.

The Bottom Line

HTC’s Titan is a smartphone worthy of its name. More importantly, it is also worthy of consumers’ consideration because it really is a fantastic device. The hardware and build are class-leading, the display is bright and clear, the 8-megapixel camera captures gorgeous images, and the Windows Phone 7.5 operating system is a breath of fresh air.

Size matters. For me, bigger isn’t always better and the Titan’s towering stature is a turn off. Many smartphone buyers enjoy large handsets however, and if you fall into that category I sincerely doubt you’ll be able to find a better Windows Phone anywhere in the world right now.

AT&T will launch the HTC Titan some time this fall.