She's so wooden and is too put-together in a way. Any role requiring an ounce of roughness, grit, or quirkiness is terribly wrong for her. That's the main reason I can't stand the idea of her as Elphaba in the Wicked movie. Act One needs the quirk and tomboyishness, Act Two she's glamorous, but she's still kind of gritty (in the best performances, anyway).
Sorry to derail, I just have a strong STRONG opinion of her.