I'll echo the above poster: Tablets do not replace computers.
In addition to the limitations that other posters have mentioned (lack of printing being the biggest obstacle), here's proof positive: My college daughter cannot access her school account on my iPad. This account holds information on her schedule, her financial account, her housing information, her grades. If she had only an iPad, she could not even register for classes.
My daughter says she has not found her laptop a good tool for taking notes. In fact, she says she has to sit on the first or second row in class because if she sits farther back, she is distracted by all the students who are playing games or messing around with Facebook in class. She says a laptop is essential to any college student, but it is only a distraction in the actual classroom.
Don't get me wrong: I like my iPad, but it isn't a full-fledged computer. I suspect that it won't be long 'til we have new, enhanced versions that will be capable of more applications, but it won't be while today's college student is still pondering this question.
Off-topic: Since when does a laptop, which weighs about as much as a good-sized textbook, require "lugging", especially when we're talking about a young, healthy college student?