OOTP is like the second best HP movie after POA. I don't like literary purism or slavish adaptations.
I'm don't either. Sometimes they change and cut some stuff and it turns out great and coherent (see Hunger Games), but in OOTP and HBP they skipped some parts crucial for character development. It was a visible laziness.
I'm trying to think of one but I can't really think of book adaptations that made me angry. HP adaptations were fine; left out some good book scenes but having them all be 3+ hour movies wouldn't work.
Book to Film- Angels and Demons
Game to Film- Mario
Manga/Anime to Film- Dragon Ball Evolution
Comic Book to Film- almost every 20th century marvel films.