I've been running it since 10.1 came out and it's been just _fine_. I think OS X itself has crashed twice in that time. I've gotten to the point where I have maybe two or three applications that require Classic (OS9) and everything else is OS native.
Only thing I'm waiting for is Photoshop 7 (beta is out already) and Quark Xpress.
All in all, totally cool. Most stable OS I've ever used.