The stock Messages app has grown dramatically, too. In addition to firing off standard texts, you also have the option of linking it to your Skype account for more of an all-in-one experience. Well, more or less. From your point of view, SMS and Skype messages are folded into the same threaded conversation. Unless the person you're talking to also has a Windows 10 phone, they'll just get those messages in two different places. You might also notice a curious blue nub in the corner of the keyboard while you're thumbing out those messages. Think of it as a software version of little red nub on ThinkPads: It's meant for fine-grained control over the cursor, but it moves so slowly I basically gave up on it.

Microsoft went big with its Edge browser on Windows 10 for the desktop, so of course it did the same here. To give you some context, Edge on the desktop was a marked improvement over the beleaguered versions of Internet Explorer it replaced. Here, the improvements are less dramatic. Pages load snappily over LTE, and scrolling through them (even really long ones) is generally smooth. Beyond that, though, there isn't a whole lot to say; you can save articles to a Reading List where they'll be converted into a handsome file with larger typefaces, and your favorites still get synced across devices when you're logged in with your Microsoft account. And of course, everyone's favorite Halo-inspired digital assistant Cortana is here too. Rivals like Google Now and Siri have benefitted from years of iteration and augmentation but this version of Cortana is plenty capable. The line between this version and her desktop counterpart is reassuringly thin, and that's mostly a good thing.

All of your email will pass through Outlook which means you can kiss pinning individual email accounts to your Start screen goodbye . Full disclosure, by the way: I'm a huge fan of Outlook on other platforms, but this version just isn't as feature-rich. Setting up the email associated with your Microsoft account (you do have one, right?) requires zero work, and even adding my weirdo corporate Gmail account with its separate security layers took just a few moments. Triaging those missives is easier now too thanks to the gestures Microsoft picked up from its acquisition of Acompli last year -- a swipe to the left archives an email while swiping in the opposite direction flags it for later perusal.

Even better, Outlook now lets you attach honest-to-goodness files (that is, things that aren't photos) to emails! It's the little things, people. Speaking of little things, here are a few more. The icons for friends and contacts in the People app are circles now instead of square, which is surprisingly jarring. You can now clear out all the notifications in the Action Center with a single tap. And certain notifications -- like those for Facebook updates or text messages -- let you respond without having to open the associated app. Three words: It's about time.

Then there's Windows Hello (still in beta), which uses a tiny infrared sensor to peek at your iris and verify your identity. The setup process basically just involves lining up your eyes in an on-screen box while Microsoft's algorithms do their thing -- just remember to take your glasses off the first time you run through it. That's right, first time -- you can run the setup multiple times to give Windows a better glimpse at your eyes in different conditions, like when they're sitting behind a scuffed pair of Warby Parkers. The practical benefits to Hello's iris scanning are still very limited; you can use your eyes to unlock the phone instead of punching in a PIN or got authorize purchases in the revamped Windows Store. It's never faster than just entering a numerical code either, which is frankly silly. At least it's accurate (even with glasses), especially once you get a feel for how far away from the camera you need to be for it to work.

When you screw up enough times that Hello gets blocked though-- and this will almost certainly happen -- you'll be asked to enter your PIN to reactivate it. Fine! Except by default, Windows 10 doesn't prompt you for a PIN for 15 minutes after you've already entered the phone. That means if you just leave all options as they were, you'll either have to wait 15 minutes or go back into the Settings, set the screen to lock immediately, lock the phone and unlock it again to make Hello work again. I'm not holding this inelegance against Microsoft (too much) since it's still a beta feature, but yeesh. I hate to say it, but that lack of polish is a running theme so far in Windows 10 Mobile.

There's a slight, noticeable pause when you swipe in and out of the app launcher. A few times, the 950 completely locked up while trying to fiddle with the screen's brightness; not even the sleep/wake button did the trick. Good thing I could remove the battery. When checking my email in Outlook, I'll sometimes be brought straight to the accounts settings menu for no reason I can figure out. My homescreen tiles once disappeared entirely after Windows took 45 seconds to launch an app. The list goes on. These are little things, certainly, but together they mar an otherwise strong step forward for Microsoft. After my days of testing, Windows 10 Mobile is equal parts functional and frustrating. It's perhaps unfair to compare brand new software to Windows Phone 8.1 and the extra year of development and polish it got, but there were definitely moments when I missed the snappy cohesiveness of the previous version. We'll soon start to see some of these rougher edges get sanded down via update, but until then, there's one more feature that might make this all worth the trouble.

Continuum

Using the Lumia 950 to power full-size apps on external displays is most interesting part of Windows 10 for mobile, though even Microsoft's brass admits some people will never, ever use it. And you know what? When it works, it's pretty brilliant.

When you fire up the 950, you'll spot a big Continuum tile on your homescreen, but you might not even need it. It took mere seconds for the phone to realize I had connected it to Microsoft's $99 Display Dock over a USB Type-C cable. With just a few taps, I was looking at what amounted to a Windows 10 desktop on my monitor. It's obviously not a one-to-one translation of the typical Win10 experience, though; instead of the Start button and search bar, there's a quartet of icons. The back and search icons are pretty self-explanatory, and indeed, you'll be using the Windows one most often. That one launches the "Start menu," or in other words a replica of your phone's normal homescreen. Click over into your app list and you'll find a majority of them are greyed out; the ones that aren't are what Microsoft calls "Universal" apps -- that is, applications with a single codebase that intelligently expand and contract based on the display they're on.

For the most part, the ones Microsoft built in-house work well. The stock Weather app uses all that extra space to show off the week's forecast, plus an hourly breakdown and additional details for the day. The grid of stories that seems so constrained in the Money app's mobile view suddenly has room to breathe and it's beautiful (if a little overwhelming). Ditto for the included Sports app, which I can't really decipher anyway. Microsoft's mobile Office suite is perhaps the biggest argument for using Continuum because the apps often work so damned well. I wrote this entire section on a full-sized USB keyboard connected to a phone connected to a television. That sentence wouldn't have made a lick of sense just a couple years ago, and now it feels like the most natural thing in world.

Are the Word experiences (or the PowerPoint, or the Excel) full replacements for their desktop equivalents? Maybe not. Still, the ability to craft a letter or a decent-looking slide deck on a big display and pick things up near-seamlessly on a small screen after disconnecting everything is a pretty powerful argument for Continuum's existence. Right now, there are two big problems. First is a slight sense of inconsistency. Still other apps on the 950, like the calculator, are just stretched out versions of the normal, mobile view and are pretty lame. Thankfully, you can use the phone to run apps and take calls while it's connected to a secondary display. Sure enough, you're better off running those non-optimized apps there instead.

The bigger problem is capability. Microsoft seems intent on demolishing the barrier between a mobile-first and desktop experience, but it just can't do it without help from developers building the universal apps that would make Continuum shine. I'm told the interest is there -- too bad there aren't many great universal apps at this early stage. Among the standouts: Amazon's Audible app (I've got a Robert Heinlein audiobook playing as I write this) and CBS's. On the flip side, the Windows Store also plays host to Universal stinkers like Facebook which just blows out the mobile view again. Here's hoping Microsoft can persuade those app creators on the fence. This feature deserves it.

Alas, Continuum doesn't handle everything the way I'd like it to. Let's say you're pecking out a lengthy something in Word and you wander off to make a sandwich. By the time you return, your phone will have likely gone to sleep, and when you wake it up to pick up where you left off, Word has disappeared from your monitor. The lack of persistence might not be an issue for some since you're meant to be able to yank your phone out at any moment, but it makes sessions of prolonged productivity trickier to manage. Your best bet is to set the phone to never go to sleep, which can be problematic in its own way.

Microsoft originally sent Engadget what appeared to be a defective unit. It had some serious trouble with input devices and Continuum. On a few occasions, Windows didn't know what to do when I was using a mouse's scroll wheel. Sometimes it would cycle through tabs in Edge when I was wanted to read more text. Other times it just stopped working completely. This was the case with multiple mice too, by the way, including Bluetooth and wired models. Thankfully wasn't an issue with the second unit I tested.

If you try to launch an app that isn't Continuum-friendly, Windows will offer to launch it on the phone instead. In the case of media apps like Spotify, the program and all its controls still pop up on the phone, but the audio will route through your display's speaker (if it has some, that is). Well, almost all the controls. If an app has key functions located very low on the screen, the "Tap to control your display" bar that sits atop the regular interface might push them down too far to see. I've haven't come across any apps that have been made completely unusable by that pesky UI flourish, but some come close; only the top third of Spotify's playback controls were visible and they were tough to properly poke. Like the rest of Windows 10 Mobile, Continuum is far from perfect and suffers from a dearth of stand-out third-party apps. But as with the rest of Windows 10 Mobile, there are glimmers of promise that could give Microsoft a distinct edge as we step further into the post-PC era.

Camera

Nokia's love of photography manifested in devices like the PureView 808 and the Lumia 1020, and Microsoft was more than happy to try and keep that tradition alive. The act of snapping a photo is remarkably fast, punctuated by an ersatz shutter sound and a brief darkening of the screen. Resulting snapshots tend to look incredible by default on the 950's pixel-dense display, with bright poppy colors and loads of detail to pick out.

The real magic, though, happens after the photo's already been taken. Pop into the camera roll and Windows will mention it's applying some finishing touches to the most recently taken photo. A moment later that photo will subtly change (usually for the better) as Windows takes the edge off overexposed spots and restores a touch of reality to colors that sometimes feel overmagnified. Very helpful. That's not to say that immediate post-processing is always a good a thing; I snapped a few shots of an L figurine under some diffused lights and the colors were crisper and more dramatic before the camera app decided to wash them out.