I liked that a great deal. I think Capaldi is just the bees knees. Loved the little thing about him looking like a magician. It felt a bit more Tennanty in some ways... I mean the whole thing being about saving a species. One of the themes for ten was that he just bloody cared so bloody much, he was a big old bleeding heart(s). I didn't especially get the sense that eleven cared a great deal (I go back to one of my pet hate episodes, the one with Diana Rigg... that little alien thing at the end, ten would have flown it to its homeworld). I don't think the doctor has to care, necessarily, but I like it when he does. I like the tension between caring and knowing that some things can't be resolved, and him looking like he's a bit of a bastard for not doing anything, but only when it's accompanied by him knowing he's looking like a bit of a bastard and there's some kind of, well, yeah, tension to it all. Unless he's written specifically to be a bastard, in which case that's just another facet of his personality. But eleven wasn't written to be a bastard, and there was never really that tension that ten had sometimes.
Anyway, waffling... I liked this episode.
I'm noticing a trend of women baddies on the show all being styled in the same way. I can't lay this squarely on the shoulders of the all evil Moffat either, it was there during RTD's reign as well. Are we that pathetic as an audience that we can't be expected to understand or read a villain unless she has a sharp, schoolma'amly and/or dominatrix vibe going on? Hair usually up, or pinned in some way, often glasses, sharp makeup, businesslike suit... It doesn't happen all the time, but it happens suspiciously often.