Battery life -
If you're going to be traveling or whatnot, in an unusual circumstance where you need more than the standard 6-10 hours (depending on model) of life . . . buy a damned battery pack. They give you a hell of a lot of extra life, and if you're traveling, chances are you have a bag or something, the pack won't be a portability hindrance. (If I'm walking to class, I don't want the extra bulk. If I'm on a plane or train, I don't really care how big the iPod is, as long as it's manageable.)