Just got back from seeing Half Blood Prince. It's just as good as the last movie. A lot of painful omissions from the book, but the movie does a fairly good job bridging the gaps.
I'm still not a fan of the director though. I'll admit that he did a better job on this one, but I still feel that 3 and 4 are the pinnacles of the series. There's simply a lack of grace to Yates' technique and it shines painfully when you contrast the emotional impact of the main death scenes in last three movies.