Yeah, the movies aren't the same as the books. There are things that work in books, but not in movies, and vice versa. Also, the 4th-7th books would be 4-5 hours long if they were faithful to the books. And while I wouldn't be complaining, that would just be silly. The movies aren't supposed to use the books as direct scripts. They take the books as inspiration and tell the story their way. Take the scene in the 6th movie with the bridge. First off, totally awesome. Secondly, in the books, we hear about it through conversations and news, which makes sense since we're reading the book. In the movie, we see it. It fits well, and adds suspense to the movie.
Another example of them making things better for the film's way of doing things: having Moody/Crouch Jr. be out of Polyjuice Potion as he talks to Harry. I thought that was a brilliant way of getting the tension back up after the relative lowering with Harry's return. In the book, it might have made the scene more confusing to read about, but it can be more easily incorporated visually.
The worst two omissions in the entire movie series so far: the Quidditch World Cup and the battle in Hogwarts at the end of 6. The game was like, here it comes, here it comes, the game starts... it's over and we're in the tent. Ouch. That hurt me. And that battle was one of my favorites. At least the one in 7 will be like half of the second movie's length, which will be epic. Possibly my favorite extended scene right there. So darn great.
