I've got a 12 inch iBook G4 and I can stretch the battery life out to 6 hours running only Word, which is good for note taking with consecutive classes where there's no way to recharge in between. So it also depends on what OS you want to be using. If you're just looking for a work computer, or you're in graphic arts or film, maybe the iBook is the way to go. It's rather cheap in comparison to many of the noteable brand name PC laptops, and I believe it's still one of the most power effiecient on the market.
Also, I carry my laptop everywhere. It's just a little larger than an 8x11 sheet of paper, and fits in my backpack easily. And yeah, occasionally you'll catch me playing Unreal Tournament or Soul Blade during class
Dont let all the rumors and misconceptions about Macs completely rule them out as an option.