I didn't mind the first two Harry Potter films (I saw the first movie then decided to read the books). They at least seemed magical. The place is supposed to be this wondrous wizard world and yet in the last two movies, especially POA, it comes across as the some sort of depressing graveyard.
Trying to change Dumbledore's character was a big mistake. Once someone testablishes a character, the audience usually identifies with that intepretation. Character murder was particular noticeable in POA. None of the new characters lived upto expectations.
If I recall correctly, when I saw The Chamber of Secrets (best one so far) at the movies they had an intermission. It is possible they might make a movie longer than Lord of the Rings and stick an intermission in the middle.
But they have to make it so kids can stand sitting through it.
And Damn Warner Bros.