It's kind of a bad thing when Paris Hilton's performance is the best one in the movie. (To be fair, it was a very good performance for her.) Repo: The Genetic Opera tries for a slick, gaudy, splatterpunk musical, and it succeeds in being about one-quarter as awesome as it thinks it is. Alas, that's not enough to elevate it above a "Meh, not so good," movie. The graphic novel pages they use to explain the plot are awesome; the movie's main action, not so much. Exception the first: If you're into fetish costuming, you should see it--just try to ignore the badly scripted dialog, er, lyrics. Exception the second: This is your movie if you think seeing Giles from Buffy being dark and evil (but with a heart of gold) would be super-hot.
If you have the urge to see a dark musical, see Sweeney Todd instead. I give Repo a C-.