This is one of those movies, that I will be buying on DVD, and if some friends suggested we go see it in theaters, I would go see it again. The cast was outstanding, the movie was funny, and the rollerderby was awesome!
Disclaimer: I've never seen real rollerderby in person, so I don't claim accuracy.
It's been a year since I read the book last, and so I read all of the books up until this one before the movie, but held off re-reading HBP, and because of this I found the movie VERY enjoyable. However I'm guessing had I read the book directly before hand I may have been disappointed. So if you don't read the books, or haven't for a while, I think I can say for certain that you will love this movie! Otherwise you're own your own!