It certainly had its moments, but man, what a letdown. For the most part, it tried too hard to be random and weird at the expense of what makes the show great.
ATHF works best when it keeps the characters' personalities consistent and gives them time to interact with each other. It also works best when episodes are based around characters who consistently produce funny dialogue. One of my favorite episodes is Revenge of the Mooninites, in which a belt with the super powers of the rock band Foreigner wreaks havoc upon the Aqua Teens and Carl. The idea of the belt is randomly silly, and it works because its effects are visualized in amusing ways. And the character interaction is ace.
For the most part, the beginning of the movie was great. I'm not going to spoil the opening, but I will say that it is a hilarious twist on typical pre-movie material. Afterward, the movie came off like the start of a good episode with a silly yet coherent plot setup and the Aqua Teens bothering each other while trying to get the exercise machine going. There was still good character interaction after the machine got going, but the movie became more and more random and less funny. I got tired of the Ghost of Christmas Past's stories about the exercise machine, the deus ex machina character skin switching, and the tangled explanations of the Aqua Teens' origins. I would expect something like that to be self-contradictory and unresolved because that is the nature of the show, but I would also expect it to be amusing.
The character selection could have been much improved. The movie overused Dr. Weird and the robotic Ghost of Christmas Past, way underused Carl, and introduced a character who really wasn't that funny (though I did appreciate that his sidekick was Neil Peart of Rush). At least the Mooninites and Plutonians had some good dialogue.
All in all, it wasn't a bad movie, but I thought it was going to be consistently funny. I laughed the most in the beginning and got more and more bored throughout, and the rest of the audience had similar reactions. It seemed like the authors didn't know how to extend a basic plot to movie length. It would have worked better to come up with another good episode plot and segue into that instead of being random and confusing for the sake of such.