My opinion as I debate the same issue:
Rarely have I found a laptop productive for taking to class. It's more difficult, in my opinion, to take notes digitally than it is to simply write down the highlights of a lecture on a pad of paper. In fact, a laptop tends to be a large distraction; with IM, FaceBook, Google all at your fingertips, it's hard to think your mind won't wander from Dr. Heavy Accent's intro to Chemistry lecture. While this could just be me, I remember things much better when I write them down. Typing just doesn't do it for me.
It's my opinion that you cannot 'study' with a laptop. You can write a paper on one, but studying requires reading a text and reviewing notes while making supplemental additions to what you took in class. Most of the time I see people 'studying' with their laptop out, he or she is screwing around.
Now, having a laptop can be fun, too. You can take it to your friends' dorms or to the library to write a paper. What you may find, though, is that you will want to seperate yourself from the computer when chilling with friends. Why not grab a brew instead of browsing a forum? And that library, well, chances are there are plenty of computer workstations that you can write your paper on.
Of course, there are times when portability becomes a necessity, and I think the option is a high priority for college students. But, you don't need a $2,000 laptop to be portable. Think about fixing up your iBook or buying a used Eee PC on eBay instead. That way you can take your laptop somewhere and not be a nervous wreck about it being stolen or broken.
That being said, I still can't decide which to remove from my shopping cart; the MacBook Pro or the iMac.