I haven't encountered a BSOD anywhere in all the machines I work on in at least 5 years. But I did skip Vista entirely. 64 bit Windows 7 seems mostly excellent stability wise, although I could list a few exceptions to this (Super (video converter) seemed to bring down my internet connection yesterday until I killed it), and I could make a huge list of usability gripes with it that I can't for the life of me figure out why MS doesn't fix.
But generally speaking I'm pretty happy.