Woah, the Christmas special was AWESOME.
It explained everything perfectly.
I cried when handles died, though.
Also, that was one firey (reset?) from old 12 to younger 12.
I guess it made up for the lack of action in the tease that is the regeneration from young twelve to the 1st (??) Doctor.
Edit: Did anyone get the 4th doctor reference? At the end of the 50th, {the fourth doctor tapped his nose while saying "who knows".} I'm not sure at what point in the episode, but the oldest version of the 12th doctor did this, I can't remember what he was saying, though.
Also it turns out that only the Matt Smith doctor remembers the events of the 50th anniversary, because he recalled on things that he did/learned in that special.