Rarely does a series finale deliver. I'm not just talking about Who, but in general, across the board, in all of TV land. And this did. And then did some more. You know you watched something special when it slips to the fore of your conscious days later, triggering a plexy of excitement and anticipation for the next episode. One so far off in November.
My favorite part was the reveal of where the opening scene of the episode was taking place. This was closely followed by any tidbit that expanded on the mythology of Doctor Who and his universe. And that includes the twist ending. Got to love a story that in its last part giving an ending that results in you reinterpreting everything that came before. Classic Moffat.
Incidentally that's also the definition of a joke. I hope come November we don't find out this is one deux ex machina themed one. But I got a feeling it won't be.