If you a blindly loyal HP groupie, then you'll love this movie. Given that caveat, it should be noted that the movie takes great liberties in the telling of the Half-Blood Prince story, adding scenes that were not in the book, changing MAJOR plot points, and in general, feeling very disjointed in its storytelling. The costuming and set design is fantastic - but that can also be said for 1992's Batman Returns. You need a story to hold it together, and HP&THBP falls on its face in that regard. The Quidditch scene is terrific - but not terrific enough to redeem this shoddily-told story.
Definitely more geared to the kids, but lots of fun for the fanboys too. Something to keep us entertained until Lucas decides to get off his butt and make Eps VII, VIII and IX