While it would be weird to see him play the Doctor, the fact that he's the oldest since Hartell is giving me goosebumps. I wanted the next doctor to be an older one again, to bring some intellect back to the show, and hopefully that's what happens.
As for DoTD, I liked it. Excellent episode, but very spotty for me. The zygon subplot could have been tied up in a better way, the whole Rose thing as well should have been better explained, even if I understood it in the end. I love how it tied into End of Time though, and I just can't wait for Time of the Doctor. I might sound harsh, but I'm glad to see Matt go.