I think Smith's excellent. I love the nods to the previous incarnations too, and the insistence that this is the same man only with a different body and characteristics. There's a moment in the big bang, where the Doctor is talking to Amy and he looks so tired, and so beaten up, that I could totally believe I was looking at a man who'd lived 900 years.
He's a phenomenal actor. I doubt he'll hang around in the role for too long though. We'll be lucky to get another two years out of him.