Good moment, yes. It does seem to be a disease of this show that the second half of two-parters are never as good as the first, doesn't it? Maybe that's inherent in the form - the first part is all build up and anticipation which the second can never live up to.

I might edit the post or write another one, but something which is worrying me (as I think it did last series) is the fact that audiences are going to start switching off in droves if things don't start to make sense soon. I read one article last week (in the Grauniad or Telegraph I think) which said that the show risks losing (or possibly even alienating) the casual viewer. I reckon it's at even greater risk after this episode, which didn't really answer amy of the questions set up last week.
I haven't had a chance to rewatch it yet, but my usual form of Moffat-itis is setting in and I feel more and more unsatisfied the more I think about it.

Also, I've seen a fair few comments/posts so far about the "ethics" of the Doctor in basically turning the human race into murderers. I need to rewatch to get it straight in my head about that.