So we start with the Doctor sulking. A lot has been made of this in the build up to the episode but really its just an excuse for Matt Smith to play a little more "First Doctor" grumpy, and even then it doesn't really last long before normal service is resumed. As ever, its a reminder that Doctor is never going to be consequence heavy, and will be content to nod in the direction of such things but - as with the Ponds brief-lived "marriage on the rocks" - its not somewhere its going to want to spend a lot of time. Especially over Christmas.
So, the perky Victorian barmaid-cum-Nanny (with some nice Mary Poppins nods) brings him out of his torpor where a motley bunch of supporting characters have failed. Returning from "A Good Man Goes to War" we have Sontaran Commander Strax, and Silurian Madame Vastra with her wife/assistant Jenny, played largely for laughs and a bit of exposition before being lost in the running and shouting. Strax in particular is a complete scene-stealer, and gets all the most quotable lines of the episode.
To be fair, pretty much everything gets lost towards the end in the running and shouting. Its a pretty bare-bones story, but a quick-witted and fun one, ideal perhaps for it's earlier transmission time and slightly sloshed audience. I think it lacks the power (and central performance) of "A Christmas Carol", but is less scattergun than last year or indeed many of the RTD era episodes. It also serves to setup the second half of the series quite nicely, with an interesting hook that I hope isn't too much of a let down at the end.
Also the trailer featured the promise of more Strax, so there's that to look forward to!