The movie feels very rushed, the same way those disclaimers at the end of radio commercials do. If you already know what's happening you can follow it, but only if. I don't care for the "new look." I thought the art direction on the first two movies was exactly right. The new thing has too much of the "dark carnival" shtick going on, complete with shrunken heads and leering hunchbacks. I don't particularly want to see "Rocky Horror and the Prisoner of Azkaban."
Also, only one minute and 45 seconds of Quidditch. What a gyp.
One big plot problem: What's the deal with the "Grim in the sky" bit at the Quidditch match? The whole point of the Grim was that Harry was seeing Sirius -- particularly at the Quidditch match, Sirius was in the stands, which is why the dementors showed up on the pitch. Having a random apparition followed by a random dementor attack just throws all logic out the window.
And why cut out Lupin explaining the origin of the Marauder's Map? There's a lot of important backstory that was just plain deleted.
In all, disappointing; which is a shame, because PoA is my favorite book of the series.
Edit: I should mention that the dementors were very good. I thought the "freezing" effect was a very clever way to depict cinematically the "creepily sucking the warmth out of you" feeling described in the books.