Although I generally hold Steven Moffat in high regard - thanks in no small part to the brilliant "Sherlock" - this episode to me marked one too many Doctor Who stories resolved by something of the form: "humans showing a deep emotion is all-powerful". Don't get me wrong, I have no beef with a "love conquers all"-type ending; I wouldn't be watching Doctor Who if I did. My point is that I don't much like it when a big complicated crisis (typically the impending doom of humanity, planet Earth or even the entire universe) is literally and *directly* solved by something like "a mother's love", or "children crying", or everyone just wishing really hard. Why? Because it's cheating! It's lazy storytelling. It's a deus ex machina where even the deus is poorly worked out, and it means you don't get a satisfying return on your emotional investment in the plot.
So it is with this story. One gets the feeling that Moffat wasn't that interested in writing a plot for the episode to begin with. It seems like really all it was about for him was getting to the end, where we are introduced to the mystery that will presumably form the story arc for the next season. And then he hastily fills in the rest of the episode with some vague christmassy threat, only to dispel it all too easily and through very little involvement of the Doctor.
I don't want that, Mr. Moffat. I want you to care about individual episodes as well as about big, clever, season-spanning mysteries. But perhaps even more so, I would like the Doctor to be a hero again, for once. Not one of the swashbuckling, gun-slinging variety (hell no: I want specs, brains and quirkiness), but simply somebody who actually properly saves the bloody day, rather than wait until something sufficiently touching happens that automatically does the job for him. He's a Time Lord, for crying out loud!
Also, new console room: meh, Jenna Louise Coleman: meh. But I'm hoping to change my mind on those two counts.