Students often are seeking solutions based on their limited space. Whether it is in a college / dorm / Uni room, or even whilst they live at home - space can be paramount. The new G5 iMac helps here somewhat - as the footprint and space it takes up seems virtually to be the same as a flat monitor which is great - and one thing that I believe will appeal to so many.
Students often like to be able to move with their hardware... I don't necessarily mean take it to all your classes, but whether or not you need to research and study in the library, go off campus for study / research, go to a study group with lecture notes / assignments, or even if you are moving away from home for school, when holidays come up and you want to be able to take your music / data / projects home with you.
Whilst I'm not a student, I like portability. Whether I am going home for a few days over the holidays to visit family, or away on a work trip, I like to be able to grab emails, work on documents, files, and I definitely like having all my music with me... without having to rely on other people computers or acces to hardware... and now I'm a mac convert - dare I say it - I might have to go back to PC and Windoze!?!??!? EWWW YUCK!
One big issue normally when talking about laptops vs desktop systems is the upgrade options. But it seems that the iMac does have some long term restrictions there anyway.
I'd go in and play at the Apple shop. I'd talk to peers and people who are maybe a year or two ahead of you - that way they have current and recent experiences to provide you with. There are some amazing little laptops in the Apple range - and refurb ones as well it seems! I was only just at a computer swap fair this morning... the whole market was not Mac except for one little stand where they had a couple of iBooks and a couple of iMac's and the guy said he can't get enough of them - that they go like hotcakes! Even those nasty coloured iBooks?!?!?!!
I love my Powerbook! Sure my uses and situation is a bit different to yours - but I think the 12" PB is a very cool bit of gear!
When are you looking at buying it?
Sometimes regardless of what common sense might suggest, or what others indicate they'd do, I also believe it is important to listen to your gut and your desires...
If I listened to all my mates - I would have never switched, and even then when i did switch my Mac mates told me to buy the 15"!
I'm very glad I didn't listen to either group!