My negative kneejerk reaction was the same as all of yours, but then I remember Dark Knight Rises. I balked at the idea of Anne Hathaway playing Catwoman. I saw her as breezy rom-com fluff who'd probably crumble under Bale's intensity. My personal choice was Christina Ricci because she's edgier. But, man, Anne Hathaway surprised the hell out of me and played Catwoman extremely well, probably due in large part to Christopher Nolan's skilled directing. So here's hoping this turns out of be a pleasant surprise as well.
Part of an actors performance hinges on a director. A good director, like Nolan, can bring extra dimensions out of seemingly mediocre talent, as evidenced above by Anne Hathaway as Catwoman. On the other hand, a director with a less skilled hand (i.e. George Lucas) can often bring out the worst in even the most skilled actors. Natalie Portman is a kajillion times better than what she portrayed in Star Wars. And even Hayden Christensen, yeah he wasn't very good in Star Wars but he was really good in other movies, like Shattered Glass.