I have been using Vista as the main production environment since the end of may 2006 when Beta 2 came out. I spent the whole summer with Beta 2, and the experience was that is was usable (I could get almost all of my work done with it) but occasionally painfully slow. But no bluescreens :)
a couple of weeks ago I upgraded (well, to be exact: reinstalled from scratch) to RC1 and I must say that the experience is totally different: It is very fast on the same hardware and everything works that I have tried so far. So, if you have the possibility to install RC1, try it out now!
Jim Allchin also has a similar message :)