On the other hand, I'm still (on 10.10.2) experiencing severe window server bug where desktop just slows down to a crawl (all animations, window switching, missing control etc. run with less than 1fps) after some time of using the machine. Rebooting the system helps for awhile... and then it slows down again.

The issue seems to be limited to only nVidia equipped rMBPs, but honestly, I did not expect a brand new laptop (I have mid-2014) for 3kEUR to stutter just running desktop animations you know?