I just tried out 2.0RC2 and noticed that clicking buttons does not make them respond in any visible way. For a moment there I thought that the button was disabled but then I noticed that it in fact works, only does not visually respond to my actions.
While this is hardly a bug (more likely an omission?) I find it very unpleasant. Perhaps this somehow went unnoticed by the devs, or maybe the designer forgot to email the gfx for button down-states? 
what buttons are you talking about? they go down here!
I believe they were the buttons next to some DSP sliders?