I found Lavender Brown to be super scary! She was just so... clingy, and... and... just plain scary. If I were Ron, I would have run into the Forbidden Forest and never come out (though she probably would have followed him).
Luna Lovegood is officially my favorite character! I never really had a favorite character from the books, but from the movies, Luna's the best. She's just so funny without meaning to be funny. ^_^
There were a few scenes in the movie that I didn't remember being in the book, and a few (somewhat important) scenes from the book that weren't in the movie. But the new and missing scenes didn't ruin the movie at all.
I think they might have botched Dumbledore's death. It just wasn't sad enough. And I don't like that they completely removed the last scene. Maybe they'll open the next movie with that scene instead, I don't know. That was really the only disappointing thing about HBP.
This movie, like its predecessors and the books they're based on, was awesome! If you haven't seen it, I suggest you go do that now. Needless to say, I'm really excited for Deathly Hallows!!!!!
Harry Potter and the Half-Blood Prince gets five Fists of Rock.