It took surprisingly little for me. The first couple of episodes he seemed distractingly young, but then I feel he's started to get the hang of how to give the impression of all that age and time behind him even as he looks young. And he has so much fun, and I enjoy how he and Amy (and Rory) work together. I've been watching a lot of Ten the past two years, since I rewatched almost everything after finishing his era, and no matter how I love him, I was quite ready to see a different take on the Doctor, and I really like how Eleven is so far.