I really loved the script, and it might be the first time in season 6, but Karen Gillan didn't keep the episode at the emotional level where it belongs. Talking about new doctor who, I'm a big fan of Donna Noble / Catherine Tate, I was surprised by Billie Piper and in the end I really enjoyed Martha Jones / Freema Agyeman. Karen Gillan is a beautiful woman, with the kind of beauty that makes you like her and think she's a funny mate: she's some material to work with, but she doesn't. As simple as it is. She didn't had many good scripts, this was one of that and she missed it, especially on the second part. Too bad.
I must say something about how the season is going on, because there's something Moffat (whom I adored as many of us with "Blink" and "The girl in the fireplace") needs to understand, or to remember. Science fiction is not science. In science fiction you can travel through the time line, in the real world probably not, for a long long time. And this is perfectly fine, but when you write science fiction you need to state some rules (your own rules of course) and respect them no matter what. Asimov stated the robot laws and there isn't a single robot in Asimov's literary universe who isn't bound to those rules. The Doctor of Moffat's era makes people see and speak with the older or younger versions of themselves, not mentioning the awful season 5 finale, where the Doctor goes back and forth and speaks to himself. When this kind of thing happens more than once I call it rubbish.