You can't really be too critical. The movie was already almost 2 1/2 hours long, to put in all that detail you are all talking about would have made the movie insanely long. The small changes didn't bother me in the least, Twilight did the same thing only a lot worse, so I was actually very pleased with how true to the books they were. I think a voice over throughout the whole movie would have gotten annoying after a while, if you read the books, you know what she's thinking. That being said, I definitely think the movie was geared toward people who HAVE read the books. I saw it with a bunch of family who hadn't read the books and ended up having to explain some things to them, but they still really liked it.
One thing I'm actually glad they shortened in the movie was the length of time they spent in the cave. In the book they did way too much kissing in that time, it was super cheesy with cheesy lines and it would have played out that way on screen. I'm glad they left it at one kiss on the cheek and one long kiss, still got the point across without all the cheesiness.