As far as we can tell, the new preview does not include any major new features. Instead, the focus is on the various new APIs that developers will be able to access to make use of all the new features in Android N. These APIs (and the Android N SDK) are now final and the company promises they won’t change before Android N rolls out to consumers later this summer.
As Google noted during its I/O developer conference, the company now considers Android N to be of beta quality and ready for daily use. Indeed, even the earliest versions of N were already quite stable. The fact that Google allowed anybody with a modern Nexus device to test it without having to go through a cumbersome install procedure probably also helped to find and squash the bugs in the last three previews.
If you’re an Android developer, now is the time to test new features like multi-window support and direct-reply notifications on Android N. As Google notes, the (recently improved) Google Play beta testing features also now make it easier for developers to get early feedback from users — including those on the developer preview.
We are still trying to see if there are any major new consumer-facing features in this preview and will update this post if we do, but for now, it’s probably safe to assume that the Android team mostly focused on bug fixes with this release.