I've been using it for a bit. There are a couple of snags, but nothing has stopped me from getting work done. Most of my issues have been with homebrew formulas that aren't updated to work with 10.10 (mongodb is the one on the top of my head). Other than that, the only real issue I've had is with installs. Each update has taken upwards of an hour and a half to install while it constantly tells me 4 minutes remaining. Post install, pretty smooth though.

Things I'm regularly using without issue: PyCharm, Thunderbird, Chrome, Firefox, Subline Text 2, and iTerm