I really didn't think this movie was going to be very good, and the only real reason I wanted to see it in the first place was because Vince Vaughn was in it, but I couldn't believe how funny it actually was. For a good half-hour straight the theatre was just non-stop laughing.
Now, of course all movies can't be great. The last half-hour of this movie was rather... slow, boring even. In fact, the movie could have done better to have simply cut to the last five minutes, which were also very funny (I really doubt anyone would have noticed the missing plot, being that the movie was just a runaway idea about sleeping with chicks at weddings).
So, if you want a good laugh, go see this movie, especially if you wanna see a lot of tits in the first few minutes.