We saw the sixth Harry Potter movie last night. It was highly enjoyable until about 2/3 of the way through at which point the edits for the book-to-film transition started coming unglued, and in fact ended up changing things on an important character level.
I can't imagine anyone who hasn't read the books being able to follow it, though. There was a LOT left unsaid.
No adaptation of a 650+ page book into a 2.5 hour movie is going to avoid cutting enormous amounts of material, and in this case, most of the cuts were fair (and some were annoying but will almost certainly be addressed in the extended cut DVD) -- until the end. They cut out some really important stuff, and changed two very important plot points, which bear directly on characters (not just plot stuff). We were annoyed by that.
However, it was an enjoyable movie, and -- especially considering how bleak the end is -- the first 2/3 of the movie was very funny. We were with a good audience for that (20-somethings mostly, at a 9:30pm showing). We laughed a lot. The young woman playing Lavender Brown is a hoot, and we loved Luna Lovegood's lion hat.
Overall? Far from the best movie of the series (I say #3, The Spouse says #4), but entertaining.