If you don't have plans to see this movie, you can check the spoilers here and then come back.
This was a perfectly acceptable dumb comedy (and when I say "dumb comedy," I mean the genre of goofballs getting into stupid situations for laughs, not in a derogatory way). It's a pretty formulaic "a bunch of crazy shit happens in the course of three dudes looking for something" plot without a lot of elegance, but it's still plenty funny with some bits that are very clever and even a few that are downright hysterical. The "piecing together the night they don't remember" bit is lifted pretty directly (whether intentionally or not) from "Dude, Where's My Car?" but is still a helpful plot-mover. The physical comedy is really well done and the leads are just some flat out talented dudes. Ed Helms and Bradley Cooper do what they do best as the dork and the asshole they respectively always seem to play, but that's kinda the clarion call of this movie: don't fix it if it ain't broke. Zach Galifianakis is the breakout here as he has a creepy awkwardness that makes you uncomfortable but also makes you just need to laugh; he really milks every line without being ostentatious about it. It's always nice to see Heather Graham and Jeffrey Tambor, but the small doses here just leave you wanting more. And man, Ken Jeong just cracks me up. Overall, this film does nothing wrong, it's simply not going to transcend its niche like "Wedding Crashers" or "Anchorman," and y'know, that's fine, it's decently entertaining and you won't come out feeling like you didn't see a funny movie (and stay for the credits because they may be the best part).