More info is out on the performance based MMR that Blizzard announced at Blizzcon. Overall it looks good to me and much less like the potential clusterfuck it did at the conference.
Probably the most important little blip in this announcement is this:
Q: If I perform really well, can I gain MMR while losing the game with this new system?
A: No. Winning or losing is still the primary factor in whether you gain or lose MMR so you still only gain MMR on a win and lose it on a loss. The performance-based adjustments just affect how much MMR you gain or lose.
This means it won’t be dramatically different. Sounds like it will help increase movement through the ranks though, which is good.