I'm especially annoyed with OotP for removing/changing a couple of my favorite scenes from the book.

- At the beginning, after Dudley is attacked by the dementor, the aunt explaining she'd heard of dementors. That whole scene/conversation made a more solid connection between the magic world and the real world, so Hogwarts wasn't just some escapist fantasy place, and I really thought it was cool. But the movie just cut it down way too much.

- The hospital scene, with Neville visiting his parents. The best scene in the book, in my opinion, and absolutely heartbreaking. Instead, Neville's parents are reduced to one almost emotionless line in the room or requirement.

- Though the twins' dropping out was visually pretty cool in the movie, in the book it was much more of a "Hell yeah!".

- The photograph of the old Order. In the book, Moody giving it to Harry, thinking it was a cool gift while explaining all of the horrible things that had happened to the other members, made Moody seem pretty messed up and the whole growing threat seem more dire. Black giving it to him in the movie made it seem a bit more subdued.

- The Order vs the Death-eaters: Flying clouds of smoke do not make an interesting fight (unless it's Lost), and completely takes away the impact of the reveal that Voldemort can fly in the final book.

I keep thinking of more, but I'm going to stop before this gets much longer.

Plus the whole thing felt disjointed and the most "greatest hits" of any of the movies. Really, OotP is the only one of the series so far that left me majorly disappointed. I did love the Dumbledore vs Voldemort fight, though.

The first two, while not great, were still fun kids movies, and fit the tone of the first books.