I would say that you will probably wind up wanting a full-size laptop at some point. Those ultra-portables are hard to do work on. Think of how small your windows are going to be when you're trying to write papers, read content online, and read PDFs for example. You'll be switching between them and they'll all be very tiny. Plus, depending on the size of your hand you might get cramps if it's a small keyboard.
I would personally look elsewhere. With a student discount a 13" Macbook is only $999 and includes a 2.1GHz core 2 duo, 1GB of RAM, and a 120GB hard drive...plus you get a free ipod. If an Apple machine is that cheap, certainly you can find a PC laptop that will be comparable for around $800 or $900.