This is a version that is ready for TESTING… more than being for daily use. The big change is the RLV fix up.
They are advising you to use this only on the Preview Grid until you are comfortable with it. That makes me a bit nervous.
In testing they want you to be sure about whether a problem is a ‘viewer’ problem or an RLV problem. You do that by seeing if you can replicate the problem in another RLV viewer. Then file the bug report in the appropriate place.