The writing was actually pretty decent for one of those kinds of comedies, but the actors were what made the movie. All four roles were perfectly cast...Ed Helms, Bradley Cooper, Zach Galifianakis, and Justin Bartha each did a tremendous job. I've loved Ed Helms since his days on The Daily Show (and now on The Office, of course), but I think this is his first major film role where he is one of the leads and he knocked it out of the park. Bradley Cooper is one of those guys who is both incredibly good looking and incredibly funny -- the perfect combo. I don't recall ever seeing Zach Galifianakis in anything before this, but he was maybe the funniest one!
Keep in mind that the movie is rated R, so it's not for everybody. There's both language and nudity, although I didn't really notice the language that much because it was just so damn funny.
Normally I don't pay full price to see movies -- I either go to a matinee or wait to rent the DVD -- because the vast majority of movies are not worth the price. But in this case it was totally worth the eight bucks!