Most of the changes in this build will be invisible to you, but we’ve made nearly 7,000 improvements and fixes to the product between 9841 and 9860. Many of those fixes were based on problem reports that you submitted in the Community forum or through the Windows Feedback app. Thanks! We also have a few visible changes that you’ll notice.
We are getting a taste of the new Action Center for Windows PCs. This means the Action Center in Windows Phone is now in Windows 10. Only basic notifications are enabled for now, with quick actions and a cleaner interface coming late
Other new features in Windows 10 build 9860 include the ability to move apps easily from one monitor to another, and animations for switching desktops. "One of the pieces of feedback that you gave us was that it was hard to know when you were switching desktops. We addressed your feedback by adding an animation to make it clear that you are switching,"
Microsoft warned however that the new build does includes some problems: the search index won't be available immediately, because it needs time to rebuild and for OneDrive to sync, and the UI design has gone “backwards” temporarily. It's harder to join a Wi-Fi network, for instance, and the interface looks more rough (especially Internet Explorer glyphs, among other things).
And finally, Microsoft has launched an option that allows you to choose how often you receive new builds. You can now select between slow and fast settings. Such a setup could allow you to get updates with fewer or more bugs, depending on how often you receive build updates.