(Spoilers below.)
I normally have a hard time staying awake during any sort of movie, but this one managed to hold my interest the whole way through. One of my friends I went with who had not read the books had a difficult time following the plot and was bored during many of the slow parts. I have read all the books and even I was still lost a few times.
I think they could have cut more than they did. They didn't need to have the scenes where everyone is introducing themselves. Non-fans won't care who they are (since you don't really see much of them in the rest of the movie anyway), and fans will already know who they are, so it doesn't add much and seems like, as Roger Ebert put it, a role call.
I didn't care for the plot points involving the house elves. The elves were basically there to be dei ex machina.
Helena Bonham Carter's character, Bellatrix Lestrange, was under-used. She is such a delightful villain that I wanted to see more of her.
I thought the first half of the book was the most boring [half] out of all the books, so I was not too surprised that the movie was not much different. Overall, an OK movie, but I would not watch it again any time soon.