My daughter just got thru her freshman year at WPI. She had a desktop and a netbook. She used the desktop almost all the time, rarely the netbook.
WPI has student work rooms around campus where the students can meet for group projects and activities. These rooms have computers in them that are linked to the campus file servers. She said that using those rooms negated the usefullness of a laptop and laptops were kind of cumbersome to take to class more than once in a while.
Her two roomates both had laptops. She said that they rarely left the room (like her netbook). They both ended up getting docking stations, a separate keyboard, mouse and monitor. My son ended up doing the same at his college when he had a laptop. (He ended up getting a desktop machine as the laptop had its reliability issues and he already had everything but the actual machine)
The usefulness of the laptop was being able to take your computer home and still be able to do work. Since we live a plane ride home, she only came home at the term breaks and therefore had no school work to bring home. She did travel with the netbook, which served her personal needs for a mobile computer just fine. Given the cost premium for a laptop (not as much as it used to be but still not zero) you can probably get the desktop and netbook for about the same price. You may even decide you don't need the netbook with all the droid and iphone aps, your phone is almost as capable as the netbook.
I also added a TV tuner card to my daughter's desktop machine. With Windows Media Center, the PC also became her DVR and TV as there is cable in the dorms. Saved on the cost and floorspace of a separate TV as her desktop machine's monitor was a 24 inch one.
In the end, some kids just liked their laptops, but she did fine and liked her desktop setup.