Back when the third movie was due to come out, I remember that I had enjoyed the first two movies, and I was really looking forward to seeing Prisoner of Azkaban. It was my favorite book, and had a lot of emphasis on my favorite two characters, Snape and Lupin, and the photos and previews that I saw looked great. Well, I wasn't so thrilled about Lupin's mustache and tweedy appearance, but that was a minor quibble.
And then the movie came out, and the entire Snape-Marauders backstory had been completely cut out. PoA is generally praised as being one of the best of the HP films, but I hated it, because my favorite part of the story had been left out. So ever since then, I've tried never to get my expectations up for the HP movies. I remind myself that there isn't enough time to fit the entire book into a movie, and I prepare myself for the probability that Snape isn't going to have much screen time. Basically, ever since the third movie, I've lowered my standards to say, "Well, if it doesn't completely suck, I'll be satisfied."
All that said, I'm cautiously optimistic. The previews look pretty good (even if the Inferi do look more like Gollum from Lord of the Rings than zombies to me), and I like what I've seen of Snape in the previews. I'm a little worried that maybe that's practically all we'll see of Snape in the entire movie, though I'm hoping there will be more. He is the title character in a sense, being the Half-Blood Prince, but since that isn't revealed until the end of the story, there might not be much of an emphasis on Snape in the movie until the big reveal.
At least we know that the Spinner's End scene will be included. I'm looking forward to that, although I have to wonder why the director/costumer/whomever decided to give Narcissa two-toned hair--she looks like a skunk in reverse! I believe she's described as blonde in the books, so I'm not sure why they went with such a weird look. I think I saw someone suggest that maybe they added the dark hair to emphasize that she's a Black, since Bellatrix is a brunette? Which still seems silly to me, but I'll forgive the silly-looking hair if the movie is good.
And they showed part of the Sectumsempra scene when Daniel Radcliffe appeared on Letterman, and it looked pretty good. It starts off with Draco crying in the bathroom, which makes him seem more vulnerable and humanizes Harry's Slytherin nemesis a little.
What gives me pause is the reported heavy emphasis on romance in the movie. The director's interviews seemed to indicate that, and the Mugglenet crew confirmed it in their report on the HBP premiere in the latest MuggleCast episode (#176). It's not surprising, since romance makes up a large portion of the book, too, but to be honest, that was my least favorite part of the book.
Anyway, we'll just have to wait and see how it turns out. I'll try to do a follow-up review on the movie after I've seen it.
Re the DH movies: I am already dreading the scene with Hermione getting Crucio'd, as I fear what Emma Watson will do with it.