Buy yourself a stack of these for class:
and then pick out a notebook with specs you can live with at a price you can afford. I wouldn't bother with a mac or a toughbook(even though I love mine!) The extra fancy won't get you the ladies so you probably shouldn't bother.
I've got a 15.4" Toshiba, which serves as my main computer these days and I love it. Its small enough that I can take it to class/work/friends without it being a royal pain but still big enough that the screen is readable. I think if I was to do buy another one I might look for a slightly smaller screen, 14" might be nice.
I suspect you'll find that hauling a laptop to class everyday is worthless if you intend to *try* to take notes on it. I don't know of anyone that actually uses a laptop for notetaking in class, its generally not practical.
I find mine leaves home the most when I go out to do study groups or homework, then its nice because I have access to email/google/etc and can look up answers or email the professor.