It's not enough for Accepted to make sloth and irresponsibility funny; the movie has to go and make them noble as well. And while I have no problem with slackers making me laugh, when they start preaching, that's when my ears close and my eyes roll.
The movie also has the misfortune of counting too much on its central character, played by an overeager Justin Long. For a film that so clearly wants to be its generation's Animal House, the comparison is inescapable: Imagine if the earlier film - recently rated by the Bravo cable network as the funniest movie ever - had counted on Tim Matheson's Eric Stratton for laughs, rather than John Belushi's "Bluto" Blutarsky, and you'll see the problem. Matheson's was an amusing character for Belushi to bounce off of, while Long's character just spins out of control, trying to bounce laughs off himself. It's an energetic performance but not an especially amusing one.