I like how all the fuss about how 'old' the new Doctor is, when he still could easily pass for early 40's -- a decade and a half younger than he is -- with the right hair and make-up. It's sort of the Hollywood effect of how celebrities always look way younger than they really are. I don't know if the change will be quite as dramatic as everyone thinks. Heck, one of the female companions could be into more 'mature' men. : P
One of the changes might be that the people that Doctor first interacts with will treat him with more respect and authority than they would 11, who physically looks like he's a grad student as opposed to a full fledged doctor.