I actually agree with all that, but now I've actually remembered a couple other things I was going to put in my last post that bothered me as well that I forgot about last time.
The Prefect thing bothered me. I mean to me it was something that bothered Harry and added to the loneliness. Ron and Hermonie were prefects and Harry wasn't. This also changed the ending conversation between Harry and Dumbledore. In the book thier convo ends with Dumbledore telling Harry he wasn't chosen to be a prefect because he thought he had enough to deal with. Once again this is one of many “small” things that add up to a big thing, like the beginning and Harry sitting alone under the window listening to the news, the arguement after the dementor attack with Harry's Aunt and Uncle, all the many things we miss out on before they leave for school. The Black family history, the Black family servant I cant remember his name. We miss out on Harry and Sirius getting closer, so much that Sirius starts confusing Harry with James, to the point where others start yelling at Sirius for it. I mean the only reference of that in the movie is once in the last battle when Sirius says nice work James, but if I hadn't read the book I never woulda caught on to that.
There was just so many, many small things that are missing from the movie that was probably considered unimportant, but by not including all those things you miss out on so much of the character building, reference to future things(the possibilty of future films showing something that wasn't explained in the past ones). When I watch a movie, I love to know all about the characters, thier past, present, future after the story. I know the films before have told us a lot, but I just didn't feel connected with this film, it all moved too fast without explaining a whole lot, it makes me very glad I read the book, because the book just took me into the story far better than the movie.