How do you turn a 870 page book into a 138 minute movie? Very carefully.
The best way to describe what was determined to be left out of the movie form the book is this: describe the book in one paragraph (5-6 sentences). Mostly everything that was left out of that paragraph was left out of the movie. Little things were added for future reference (Grawp, Kreacher, lovelorn/jealous looks from a certain girl). And I'm okay with that. Why? Because they fixed the biggest problem I had with the book.
When I was going through my Potter book-a-thon last summer, this book was the hardest to get through. Not because the book was bad or anything but because Harry acted like a bitch for the entire book. I understand that Rowling was going for sullen teenager but he came across as a whiny, "woe is me" brat. Halfway through the book, I started to hate him. So credit to the screenwriter Michael Goldenberg and Daniel Radcliffe for making Harry's attitude not as annoying and more understandable.
That said, I think they should have added the Quidditch scenes because this movie is devoid of fun and the "Weasley is Our King" scenes would have lightened the mood of this otherwise political thriller set in Hogwarts,
Imelda Staunton is the biggest standout as Dolores Umbridge. She pretty much takes over the movie. I just wish there were more scenes with her and the other British acting powerhouses in the film (Maggie Smith and Alan Rickman particularly).
The battle in the Department of Mysteries in IMAX 3D was amazing. It was a much better use of the technology than Superman Returns (the only other movie I saw in IMAX 3D). It is definitely worth the extra cash and if you are near one, you should definitely make the effort.

