The real real reasons to get a Mac:
Better security. OS X is close to impossible to break into. I have had Macs for almost 10 years now, and never had a virus.
No crashing. A program might go down, but it almost never takes the system with it. Overall, Mac OS X is a lot more stable then Win XP.
The iLife suite. With a new Mac you get: iTunes, iPhoto, iMovie, iCal, Garageband, Pages, and Keynote (among other programs, this is just iLife). All of these are great apps and can do most of the things you'll need for school. iTunes plays music. iPhoto stores and organizes all your digital photos. iMovie is basically a better version of Windows Movie Maker. iCal is a great app for keeping track of appointments and such. Garageband is for designing musical tracks, this can include live recording from an instrument or microphone, or just playing around with prerecorded loops. Pages is the new text editor and layout program. It will do everything you need in the way of typing papers and similar things. Keynote is what it sounds like, a speech and presentation editor. I've never used it so I can't say much about it.
Anyway, there are three very good reasons to go Mac.
Although, as Salada said, there are new Macs coming out next year. June 2006 isn't that far away. I know the older ones will still be supported, but for how long?