Insider Preview Build 14915 Released to Fast Ring for PC & Mobile: Announcing Windows 10 Insider Preview Build 14915 for PC and Mobile | Windows Experience Blog.
A few "known issues" in this release, such as Adobe Acrobat Reader still crashes when you try to launch it. However, the release includes many improvements and fixes. Of note is the change to Delivery Optimization:
See the blog post for complete details.
