There was a lot of good stuff in this episode, I have to say, but it suffered, really suffered, from being 45 minutes long instead of an hour. Development of characters and concepts had to be compressed into sentences, giving it overall a very rushed feel. The framework holds up on retroactive inspection, but if you missed anything, you're probably going to be crying foul at developments that you missed the foreshadowing for. It doesn't actually end on a deus ex machina, but by golly, you'll think it did for a minute.
To discuss the cybermen reboot on a separate note... yeah, they're made scary, but the thing is, I'm still wondering why they didn't keep using some of their tactics in the climax that they demonstrated in the set-up (You'll see which one I mean in particular). But Gaiman does use them creatively, I will admit.