It must be remembered that the Doctor is a Time Lord, and I think this episode just went to explain how much better the Doctor is at dealing with moving around in time than humans are.
As someone mentioned earlier, it was
kind of a reset button, but used in a good way, rather than just resetting the subject in the next episode, the Doctor actually reboots the entire Universe. I did think, on the Earth without Stars, that history would have wound out utterly differently without them (no Navigation, Astonomy, Astrology etc, and the effects they had on Humanity) but that was tiny nerd-niggle

All in all thoroughly enjoyed the episode, nice to get some consistency and a nice series-length story, kind of reminds me of the Key To Time, looking forward to the next one.
My only concern is the amount of weight being put onto the character of River Song, can't help thinking, whilst she's a great character, that creating a non-regenerating (assumedly) long-term partner for a character that regenerates may be a Pandora's box in and of itself.
Edit: Oh, and I agree with whoever suggested earlier that the oroginal destruction of the Tardis has something to do with River, or possibly even the Doctor himself