Running 71 on my spare desktop and with the exception of the known issues
http://aka.ms/uqh0df
Everything seems to be fine.
Likewise running 77 on my spare Windows 10 phone and it also seems fine.
No doubt there are some undiscovered issues, which may have something to do with third party software such as games and such and possibly even some hardware, but.....
I think, overall, these builds are getting better.
I certainly hope so, as they're still talking about a Spring 2017 GA release (maybe April) for redstone_2 and then it's on to redstone_3 slotted for Fall 2017 (maybe October).
Something to look forward to...... or not.