Mark,

I switched to os x (jaguar) two months ago and absolutely love it.
Ableton Live and Reason work without any glitches, unlike os 9.

There's a ton of free software out there to get the feel of os x, but I'm sure you're looking for more substantial applications.

Download the beta version of apple's "safari" web browser. I'ts the shit, looks just like the Itunes interface.

http://www.apple.com/safari/