here's my background...I went to school for a BS in Audio. I got through school with a MBAir, and it was great. I ran, and still run, some pretty heavy hitters like Adobe suite, Final Cut, Logic, etc. and it all works for me. However, I did upgrade my Air as much as possible (maxed out the ram, upgrades, etc).
If you wish to get the basics down, word processing, a keynote (powerpoint) here and there, then an MBAir is more then enough for you. The weight of the Air will be amazing when it comes to lugging it around campus in your backpack.
The computer geek (or jedi) in me would say that a Pro would work to, and would give you better performance, etc.
An iMac is also a good choice, as your iPad can do a lot of basic functions, and you could use the iMac as your home base. BUT, I would not trust a college dorm enough personally to store an iMac there 24/7. I'd be much more comfortable with a computer that would go with me everywhere.
In the end, it all comes down to you. If you want something light weight to compliment your iPad, go for the Air. If you want something a little more powerful, that will work wonders for you, go for the Pro. And if you want a home base, with huge potential and power, and feel safe that it will be in your dorm safely, then maybe that will work to.
----edit, i will note that if you are going to go with an Air, do the 13-inch...having the smaller 11-inch is going to feel too much like your iPad, and you may feel that it has no use.
