Are you an eight year old boy? I saw it with a few friends, and I thought it was terrible through and through.
Well I wouldn't go as far as saying it "kicked ass" but in the superheromoviegenregroup it was a solid movie. Of course, superhero movie genre has been subject to atrocities like Daredevil, Catwoman, Fantastic Four, Batman&Robin, Superman Returns etc. ad infinitum.
In this company, TMNT movie is a good one. Batman Begins is better, Spider-Man 1&2 are better (still haven't seen the third...), but that's about it of the more recent comics based movies. Compared to all movies, it's more or less mediocre I have to admit. Compared to all animated movies, there are a lot of better movies and some worse.