No beta testers are going to be able to comment on anything specific, as it would violate NDA.
That said, as a beta tester myself -
All I will say is that there was enough broken in 2016 that I still haven't deployed it to my users, and only recently bothered to install it for myself (+/- Thanksgiving 2015? Some time after SP2), to see if the more critical items had yet been fixed.
That is why I only attempted to use XREFOVERRIDE last week for the first time. Haha
It's funny... but it's really not... but it is though.