Overall, I thought the movie was really well-done, especially since we are talking about the longest book in the series. The movie does capture the bare bones of the plot, including a few things that do come in later (including a character JKR warned them not to take out because of the role in DH), and even some additional things that aren't set in canon that may foreshadow events in DH. In the possession scene, when Harry says he has to feel sorry for Voldemort? That definitely wasn't in the book. But Dumbledore did show Harry a ton of stuff about Voldemort's past in HBP, so now Harry has to piece all that information together and figure out how that information is useful. It could very well be that he has to feel sorry for Voldemort (or at least learn to relate to him, which he has already done on some level--remember in CoS when Harry meets Tom Riddle's memory, and Tom points out that they're quite a bit similar?) in order to defeat him.
I was talking about the movie. Yes. Evanna Lynch is the perfect person to play Luna. Luna is one of my favorite characters in the series, if not THE favorite character, and I absolutely love her portrayal in the movie. I wish they did do they Quibbler article, if only to see Rita Skeeter again, but ah well. I do like the other way, too.
Speaking of which! Snape. Ohhh, Snape. He was so deliciously maliciously evil in this movie. I was sitting there "YESSSSSSSSSSS"ing the entire time, especially when he refused to give Umbridge the Veritaserum.
OH OH OH. Why on earth was Cho the rat, and not Marietta? Fine, so making Cho the rat cut out the date, thus cutting out the Rita interview, et cetera. And now that I looked it up in HPL, she doesn't show up in HBP. I was thinking she did only once or twice minorly, but that'd probably get cut from the movie anyway. :P I'm such a bad fangirl.
Speaking of love polygons, Ginny was definitely not dating Dean at the end of the movie unless Dean pulled a Michael Jackson. So come HBP movie time, Harry's going to have a crush on Ginny, and then he'll find out they're going out by walking in on them kissing.
And how could I forget Bellatrix? Her voice would annoy me if she were a major character, but for Bellatrix's role, it's perfect. And by perfect, I mean perfectly deranged.
And the Ministry of Magic... WOW. It's not how I pictured it in my head (I was thinking more purple myself, but we are talking dark days here), but it looks fantastic. The Atrium reminded me way too much of 1984, though.
So we didn't see the entire battle or all the rooms we saw in the Department of Mysteries. Understandable since it's a movie. I'm disappointed in one thing re: The Battle. Why was The Locked Room not mentioned AT ALL? If it (or at the very least, the contents, but wasn't there something about the Department of Mysteries showing up again? JKR didn't say no to that question) plays A Huge Role, it better get mentioned in the HBP movie. Just saying.
I love Grawp and the centaurs. Just... love.
OH. Sirius gave Harry the two-way mirror, and we know that Harry never used it. But in the movie he never broke it, as it was a piece of paper instead of an actual mirror. Ten days until (maybe) the mirror comes back.
Overall, I loved it, although a few scenes in the beginning felt a little forced. Luckily, this got a lot better as the movie went on.