I can't say much for AppleCare itself (I'm still waiting for new updates to get my PowerBook!!!), but as a soon-to-be third-year in college and owner of a Dell Inspiron laptop, I can tell you that buying an extended warranty is a VERY good idea. I lug my laptop to class everyday and use it extensively for taking notes; as a result, my Dell's enclosure now has two cracks and a missing key, as well slight scratches on the display. I bought an extended 3-year warranty on my Dell, and after a few minutes with tech support, they offered to repair all the nastiness of my laptop for free. Granted, Apple's notebooks might be a bit more rugged, but any laptop that's used in college will take a beating, and it's good to have a warranty to back it up.
Plus, a recent PC Magazine article rated Dell's and Apple's service/support as the highest, so if Apple's is anything as good as Dell's, I say its a good buy.