I got to say the new Doctor doesn't really seem to fit the part. Maybe it's because I've only really known the last one, but it seems the Doctor is a character that is suppose to have a certain goofy and fun charm to him. This Doctor gives me the impression of the show taking a some what of a darker turn.
Well I have seen most the original series, 60's - 90's, in reruns, and all of the new series and each actor brings his own take on the title character. We get used to the one we saw initially and feel noone could replace him. I have seen many actors over the years play the Doctor and I felt the same way as you do when each new incarnation was presented. But as time went on I got used to it and saw the character develop in new and interesting ways.