I was quite skeptical about this one going in, because what could be more intellectually lazy than basing your Christmas episode off of the Dickens story? Dead horses, jump the shark indeed.
That said, oh it was lovely and magical, wasn't it? There's hardly any doubt that this one was the best of the Christmas episodes yet. (The only one I really like is 'The Runaway Bride' anyhow, though the last fifteen minutes or so of 'The Christmas Invasion' are great.)
Future cruise line bridges are very Star Trek, aren't they? And not any Star Trek, but the reboot with its white walled, blue gelly screened lens flairs. That Amy and Rory are dressed as a roman and a copper respectively is simultaneously perverse, a cheap trick by the Moff to get them back in iconic costumes they have no reason to be wearing, and confirms just about everything you'd think about their relationship. (It must be a lot of fun. *G*)
All of the Timey-Wimeyness makes sense, but we expect that by now from the Moff. Except that the Doctor used to have isomorphic stuff, so that doesn't make sense, AND why is it you can touch yourself without the universe imploding in the Moff era? Baffling. Double entendre a bit intended, however.
Yet. The episode primarily works, I think, because you see the exact moment where the Doctor is fresh out of ideas and decides to do a Dickens short story and see what happens. This episode is chock-full of wonderful, magical things - like the flying fish, and the idea of spending every Christmas with the Doctor having strange adventures. I assume there will be a lot of fanfiction exploring the cutaways we're shown.
AND! The most exciting thing for me was when we actually got to see a snippet of the adventure with Einstein, Monroe and the wedding chapel. I wasn't overly fond of the bit early in the beginning where Eleven has suddenly picked up Sherlock's method of reasoning - though the whiplash from that to the realization that Kazran had been hit as a child led to this funny line: "Whoa dude, we went from Sherlock to a West Wing Christmas Special in like, five seconds there."
Overall, it's gentle and heartwarming, this one. Eleven is probably the Doctor I'd most like to travel with - he's simultaneously more odd than Ten, but more human as well. A neat trick in and of itself.
And how 'bout that trailer? :D