I'll just go ahead and start this review by saying I'm glad this will be the last movie in the Hangover franchise. At this point, they really should have stopped after the first. Hangover 3 is not worth your money or your time. It pains me to say that given my affection for the first one. Part 2 was lame but at least they tried. I don't think any of them even cared about Part 3.
Hangover 3 breaks away from the theme that made the franchise so popular in the first place. There's no crazy, wild night that the guys have to try to remember in order to solve their dilema. A Las Vegas "gangster" of sorts kidnaps Doug forcing the wolfpack to hunt down Chow. And that's pretty much it. They spend the next hour or so trying to catch Chow, who somehow continues to find ways to evade them. There's no, "How did I get this tattoo on my face," or, "What's in your pockets?" I don't think anyone even has a drink in the whole film.
Hangover 3 is not funny. I barely laughed through the entire movie. I remember sitting in the theater listening to the audience, wondering if I missed something, but no one was laughing. There were a few cheap laughs but not enough to make it worth a visit to the theater. The best part of the whole movie comes after the credits. There's a short clip that is by far the funniest moment (that's not saying much). If you end up sticking around through the whole movie, make sure you stay to see it. I'm sure that scene will be on the DVD, though.