As someone who watched movies 1-6 before reading the books, I think they could done better at explaining more in Order of the Phoenix and the Half-Blood Prince. I got the general idea of what happened, but I definitely confused as to a lot of what was happening, and why. I'm kind of grateful for that, though, because that's what motivated me to finally crack down and read the books before the last movie came out. It helped a lot -- suddenly I understood everything that had happened in those two movies (and a lot of things I missed/disregarded in previous movies), but still, I don't think it's in a movie's best interest to assume everyone has read the books.

That being said, I understand why they had to cut things out for the sake of time and interest-- as a lot of the things included in the book didn't tie into the central plot (they're nice to have in a book, but would have been unnecessary and tedious in a movie), and the first four movies were amazing and easy to follow. All in all, I loved the movies-- the cast was great (and the adult cast was PHENOMENAL), the CGI was great, and the action/plot was intriguing and engaging.

Mostly because of the missing parts

I get that sometimes they have to leave stuff out, but I don't like it when they change stuff that doesn't need to be changed.

The movies are enjoyable, but the books are my life.