I agree. I enjoyed this movie, but thought it was really choppy. I'd just finished re-reading the book, which was probably a big mistake, as I realized just how much was missing in the movie. I was really looking forward to meeting Neville's grandmother and parents, and seeing Prof. Lockhart again. I couldn't believe they left out the entire St. Mungo's section, and there was no Quidditch at all. I really didn't like the ending, when Harry's 'possessed'. I remember thinking at the time what a cheap bit of film-making. And I really thought there should have been mention of Aunt Petunia's part in all this, and why Harry needs to return to the Dursley's. I think the one part that could have been deleted was the whole Grawp story; it wasn't really necessary to the story.The movies are leaving out soooo much that I doubt someone that hadn't read the books could really follow what is going on.
The fact that the book was so long really shouldn't matter. 'Gone With the Wind' is over 1000 pages; if I can sit thru 4 hours to watch it, I'm pretty sure I could sit thru 4 hours of Harry Potter. (and for those who haven't read GWTW, they actually left out a lot for the movie)