I enjoyed every minute of this film! I think it was an excellent portrayal of the essential story of the book. Now, of course, they have to cut things, and there were things I wish had been left in, but such is life.
They did an excellent job of building the relationship between Harry and Sirius, which stung as we knew what was coming. I thought the actress who played Luna was quite good; dreamy and 'off' without being "a freak". I was skeptical about Umbridge, because this actress did not look 'toady' enough, but her portrayal was incredible! It reminded me of the seething hatred I felt for her during the book. The graphics in this film were possibly the best for any HP film so far! Everything in the ministry was beautiful; I don't remember anything in the book about the characters...well...swirling when they Apparated, but the effect of the Dark and the Light fighting in midair was magnificent! And the graphics for Fred and George's fireworks display were fascinating.
One thing I definitely missed was the visit to St. Mungo's. It would have given the actor playing Neville a whole new level to see him with his parents. Also, I wish they had elaborated a bit with Snape's memory of James, or included Harry telling the others about it. It is the first time he sees his parents through an imperfect lens. All in all, a great film for a great book. They are already filming book 6. YEA!!