I switched to Mac OS X about a year ago and now have a 17" iMac, 15" MacBook Pro and aging Windoze / Linux box in my studio. The biggest limitation of the MacBook (and the reason I went with a MacBook Pro) is the graphics card (it’s pretty wimpy). If you don’t need a notebook, pick up a 17" iMac. Its a great machine and has the same graphics as the MacBook Pro, but at half the price.
I’m a big fan of Linux (have used Ubuntu and a couple other Debian builds for years now). The biggest problem with Linux is a) lack of commercial applications and b) lack of hardware drivers. If you can live with Blender, GIMP, and whatever other Open Source apps you can find, Linux is a great OS (and in some ways better than OS X, at least IMHO).
Not that there’s a huge selection of apps for OS X, but at least in video / graphics development, the selection is pretty decent. A copy of iMovie HD came with both my Macs, but to be honest, I haven’t given it a try yet. I wouldn’t say that OS X is “crash free”, but it’s been pretty close. That plus not having to bog down my machine with virus scanning apps and the like. Overall, I’m pretty happy with OS X, but with a bit of effort and assuming I didn’t need anything that wasn’t available, I could probably be just as happy with Linux.