I've used OS X for 2 weeks, but it's too quirky for basic daily use. I need to reboot to run my homebanking software (which runs inside Virtual PC), Napster is very unstable under OS X and the most important: Steinberg's Cubase VST won't run. And the Finder has lots of inconsequencies in it.
And then, when I rebooted in OS 9, I was very impressed by the responsiveness of that good old system I had started to take for granted.
And oh, the Dock takes unnecessary screen space. Under OS 9, I'm running an extension called Taskmenubar. It does exactly what the dock does, but it's always visible without taking screen space. It runs inside the menubar.