Observations, after upgrading from the previous build, on my Lumia 920 Developer Device (RM-820_nam_canada_246):
Still appears to be broken, concerning Office documents stored on SharePoint servers (that's the first thing I ever check).
Was able to install several "retired" apps from my library. Example: Microsoft Store, Today show. These were removed from the store a very long time ago. Neither of them work, probably because the backend isn't running anymore.
Lumia camera was available, however when I launch it, it just tells me it's obsolete and I should use Windows Camera.
Insider Hub is showing lots of notifications on the tile, but will not launch.
MyATT app crashes at launch (I expect to see an updated version of this before ATT will release the 950 for sale)