Windows 10 Technical Preview for phones took a big step forward today with the public release of build 10051. Whereas the last public build kept most of the Windows Phone 8.1 apps intact, the new build is much more transformational; mail, calendars, contacts, messaging, mapping, and even the Web browser all now use new universal applications.

On the one hand, this means that the new build looks and feels very different, in places, to its predecessor. Some of the work is very promising, too. For example, mapping and turn-by-turn have been integrated into a single app, which makes a lot more sense than the split approach used in 8.1. On the other hand, many of the apps are alpha quality (even going so far as to have little on-screen alpha symbols), with others beta quality (and accordingly adorned with little beta symbols).

One thing to make clear: this isn't ready for use on a primary device. As well as a list of known bugs including no functional airplane mode and the Office apps being inaccessible, I've found the apps to be quite crashy and a little weird in the few hours I've been using it. If you want to try it, use a phone that you don't need to actually use.

While it looks different in many regards to Windows Phone 8.1, the familial similarities with Windows 10 are much stronger in this build. For example, the new battery icon at the top of the screen matches the style of the one used on Windows 10's taskbar. Even the Start screen itself has introduced some odd bugs. Folders, created by stacking tiles on top of each other, are a feature found in Windows Phone 8.1. In 10, for some reason the tiny little icons now include the text labels which end up scribbling all over the icons and making a bit of a mess.

As with the previous build, Windows Phone 8.1's "use the background as the tile background with cool parallax scrolling" behavior still works, but isn't configurable in the user interface. The settings app only allows you to set a background with translucent tiles, which is much less satisfactory.

In a break with tradition, the first new app that I'll look at is the app that gives the smartphone its name, but is, for me at least, perhaps the most underused of all the major apps: the phone app. I've always been something of a telephobic, so my interest in the phone app has always been cursory; the Windows Phone 8.1 app works for when you really need it, and its visual voicemail implementation takes most of the pain out of using voicemail, but it's pretty basic. The new app doesn't substantially change the call history, and I can't currently test its voicemail support (the phones that I have installed the preview on don't work with the SIM I have voicemail on) so have no insight about that, but the dialler is tremendously improved, because now the dialler itself is searchable.

Start punching in a number, and the dialler will automatically search your phone book and show you contacts that match the fragment you've typed in. More importantly, start punching in a number that represents a name—73837 for Peter, for example—and it'll do a text search of the phone book. This isn't the first dialler I've used that works this way (though I don't remember where I've seen one like this, because the iPhone's is dumb too; perhaps during one of my stints with Android), but all diallers should work this way. It resolves the conflict—I want to call someone so should I go to the people app or the dialler?—in a sensible and straightforward way. I'm still not going to be falling over myself to ring people up on the telephone, but I'm now confident that my telephonic experience will be greatly enhanced on those infrequent occasions that I'm forced to use the thing.



















The next app that's logical to look at is messaging. We know that functional improvements are coming, including the re-integration of Skype chat, but it doesn't appear to be plumbed in just yet. What we have for now are some stylistic alterations, and a design that makes it much easier to call someone you're texting.

The People app has been similarly restyled. Circular pictures are used for profile images, with similar integration of Twitter as we've seen in the past. After using the People app a little it asked me for feedback, specifically how I felt about using my accent color (glorious purple, because it's the greatest color ever invented) as the background of the contact cards.Microsoft is craving feedback, be it bug reports, suggestions, or just plain "I don't like how this works." The preview builds even have an instant access way to get to the feedback; pressing power and volume down simultaneously starts the feedback app instantly.

The most significant feature of the most recent Windows 10 build on the desktop is the new Project Spartan browser. It makes its mobile debut in this build for phones, and it's similar to its desktop counterpart: it uses the new, legacy-free Edge engine, and a new interface. It has the same reading mode as the desktop browser, and similar settings. Other aspects, such as switching between tabs, are similar to Internet Explorer for Windows Phone.

Spartan on the phone lacks the Cortana integration that's one of the big selling points of the desktop browser. It also has peculiar omissions; for example, there's no way to switch between preferring desktop sites or preferring mobile sites. Nor is there (yet) any tab syncing with the desktop.

I'm also disappointed to see that the address bar is at the top of the screen. Putting the address bar at the bottom of the screen makes it far more accessible on a smartphone, and while I recognize that it can create some space pressure if you also want to have a tab button, refresh/stop button, and reading mode button, I feel that the trade-off is well worth it.









More radical are the changes to the e-mailing and calendaring experience. When Windows Phone was first released, its e-mail client was a breath of fresh air: a simple, elegant design that made quickly handling e-mail easy and efficient. However, the client hasn't changed a great deal since its introduction, and while it certainly hasn't got any worse, it's no longer the shining beacon of simple efficiency that it once was. The new calendar and e-mail apps have new, old, branding: they're now called Outlook Mail and Outlook Calendar.























The new interfaces are self-explanatory. The Mail app adds the swipe left/right-to-perform-action feature that is becoming increasingly common; it's a different take on the quick deleting and flagging that the current mail client offers, but broadly similar in effect. The mail editor itself is much richer, with far more control over formatting of HTML mails. Powering the mail editor is the Word engine. Although the new Touch Office isn't available in this build, clearly the working parts are somewhere inside the system. The controls use a kind of cross between the ribbon and the app-bar.

Outlook Calendar uses a similar iteration of the ribbon for tasks such as creating appointments and meetings. A traditional day view and a condensed agenda view are both available.









The apps seem solid enough, but there are lots of gaps at the moment. For example, individual inboxes can't be pinned as tiles, nor does there appear to be any kind of unified inbox. The current app makes it easy to see all unread, or all flagged mail; a feature I find invaluable, but apparently missing from Outlook Mail. I don't think these apps are far from being solid, usable apps, but they're not there yet.

The interfaces also feel like they need work. While e-mail composition puts its toolbar conveniently at the bottom, the main inbox listing and mail reading views put it unhelpfully at the top. Worse, the inbox listing puts a hamburger menu in the top left of the screen. This makes them much harder to reach. The menu in the top left is particularly unfriendly to single-handed usage. This is disappointing to see; Windows Phone 8 felt very thoughtfully designed and carefully engineered for smartphone usage patterns. The design of the new Outlook apps feels a lot less special; they have a kind of generic look to them, and have lost Windows Phone's thoughtful touches.











The last major new app is Maps. Of all the new apps, I think this feels like the best-rounded, most complete app. It integrates into a single application mapping and navigation, It seems to look good and work well, except for that blasted hamburger menu and top-mounted search bar. As ever, this would be better if done at the bottom of the screen.

The new build also gives a look at some of the smaller things that have changed in the new operating system. When the Lumia 640 was unveiled we saw a few new operating system features that are being included in an update called Windows Phone 8.1 GDR 2. It's not currently clear if GDR 2 will receive widespread distribution, but unsurprisingly, we see Windows 10 adding comparable features. Application permissions (for accessing things like location, the camera, and contacts) are easier to manage, with listings of which applications can access each feature, along with a centralized place to revoke this access.





GDR 2 and Windows 10 will also include a new anti-theft capability: "reset protection." With reset protection enabled, it won't be possible to wipe or unlock the phones without permission from the original owner. This should reduce the value of stolen phones, and is likely comparable to equivalent facilities found in other platforms.

Compared to the previous build, Windows 10 Technical Preview for phones build 10051 changes a lot. It's clearly an operating system related to Windows Phone 8.1, but the details are all very different. It feels very early. I found many apps crashed or were glitchy, and the list of known problems includes some nasty gotchas such as Internet Sharing breaking Wi-Fi connectivity in some situations. With the exception of the new Maps app, a lot of the modifications feel like they're laying the ground work for progress, but they're not yet solid improvements over what we have today in Windows Phone 8.1. Outlook Mail, for example, has the nice swipe-to-delete and a much more capable message composer, but it gives up useful pinning and inbox filtering capabilities.

There's also a great deal of interface inconsistency. While the new ribbons, for example, work well, the proliferation of top-mounted hamburger menus is a major regression compared to Windows Phone 8.1. Parts of the operating system do still have that Windows Phone thoughtfulness, but it's much less apparent, with many pieces feeling like warmed over generic Android apps. Microsoft has a lot of work ahead of it if it's to make this into a robust, reliable phone platform, and even more if it's to make it a phone platform that looks and feels coherent.