For anyone who hasn't watched yet, for heavens' sake don't read on!!
It was brilliant
Loved it, such clever writing
As for the end - hmm, intriguing, they did manage to keep that a secret!
But it might just be for one episode or so don't you think? Bearing in mind it's some sort of alter-ego/timesplitter/Drwhoish conundrum thing...absolutely terrific bit of casting though