Well, that's the problem. He CAN actually act- see one of his other few movies as an adult, such as Shattered Glass or Life as a House, and he does have mad acting chops, but in Star Wars he was made to look as if they only emotion he could convey was whiney-ness or "I am wearing pants."
I'm hoping that Jumper is somewhere between those two extremes, because I don't want too much drama in my sci-fi, but at the same time, it's good to have actors who can act.
-kv