After the release of Windows 10 version 1511, Microsoft took a few months to refactor and otherwise update the deep-down chunks of their OS. After that was all settled, they started merging features from their many teams. For the last two builds, the amount of changes ramped way up, not all of which were announced at Build conference.
These features have been merged without much bug-crushing, though. Microsoft knows this, and then talk about a “Bug Bash” event happening sometime this week. To get a feel for the state of this build's quality, though, you can check out WinBeta attempting to show off the new features. Note that some of the issues they were experiencing were actually in the known issues list, namely the crash attempting to pin Settings options, but the list is quite long.
A couple of new changes are interesting and surprising. First, long-time, multi-monitor users will like that the clock is now on all taskbars, not just the primary monitor. They acknowledge that this was driven by the gaming community, although they don't explicitly state that it's because our applications run in fullscreen mode so frequently (covering the main monitor clock). I don't exactly know why this slipped past the user experience people for so long, at least since the multi-monitor enhancements in Windows 8, but it did. It should be publicly available in July.
They will also allow desktop icons to have mini symbols (badges) attached to them. This could tell you how many unseen emails you have, whether your alarm is active, and probably many other features when it's in a publicly-accessible API. It's concerning that it's UWP-only, though. It shows that Microsoft wants to deprecate Win32 for new features, without migrating them into UWP containers, which further suggests that Microsoft intends to deprecate Win32 altogether. This is very concerning for several reasons, but I'm not going to reiterate them in this post.
The other cool feature, though, is a new interface to select between multiple sound cards. In my scenario, I have two main sound devices. When I listen to my headphones, I plug them into a USB sound card (technically a Blue Yeti). When I want to use speakers, I flip over to motherboard audio and turn on my sound system. This means that I need to go deep into the Sound preferences in the Control Panel, and it also means that some applications don't cleanly switch over (even locking up entirely). With this a front-and-center input menu of Windows 10, it should pressure developers to test whether their software can accept a sound device change on the fly, and fix accordingly.
So yeah — those are the three features that spoke most to me. Again, the lack of innovation in native Win32 APIs is concerning. It reminds me of when browser vendors declared that certain new APIs would be artificially held back from non-secure HTTP contexts. In some cases, it makes sense — an unsecure Web app accessing your webcam is a sign that they don't care about your privacy — but it also means that software developers need to give up some level of their anonymity to acquire a certificate to access those features (unless offline sites are classified as secure in the user's browser, which Google Chrome does and others might too). Tangent aside, it feels like Microsoft is trying to apply the same level of pressure to push people away from bare Win32. That makes sense, they want to promote new platforms, but it also usually comes before the old one gets the guillotine.