After growing up with Windows (dad was a software developer, had a windows machine in the house when I was born) I made the switch to mac about a year ago, and I will NEVER go back. 'Expose' was immeasurably helpful to me in the last show I was ASMing, since I had about 15 different documents open at the same time, and had to try to keep track of what was where. I would've been hosed on a windoze machine. Also, for reliability and getting back on your feet if it goes down - a mac can't be beat, especially if you're in the vicinity of an Apple store - my battery died on me one night before rehearsal. I ran (frantically) to the Apple store, where they replaced it free of charge in about 15 minutes. Beats shipping it off for 4 weeks and maybe getting it back fixed.
Note with Vista: ~250mb are taken up by security measures that you CAN'T turn off and serve no purpose. Also, it asks you EVERY FREAKIN' TIME you try to open an application. Macs ftw.