I'm not in college anymore, but observation from my senior year and visits since then seems to show that more and more people are going with the 'just a laptop' route. It helps that the school has installed 802.11 APs in most of the buildings (some with enough range to cover outdoor areas around campus as well). Consistent wireless access around campus makes a laptop much, much more useful. It's also a school with a fair number of "rich nerdy kids", FWIW.
If you're looking for purchasing advice, it mostly depends on how you intend to use the system; if you want to type papers away from your desk, or take notes in class, a laptop will be useful. Otherwise, it ends up being a more expensive, less comfortable, and more easily stolen desktop.