I liked it. A lot. And not just because of all the fanboy nods, from dropping the name 'Valeyard' to lifting dialog from previous episodes. No, I liked it because it was a barn-storming romp! The acting was great, with Smith finally getting to play the doctor as something other than a caricature, which makes a nice change for this season. And Richard E. Grant picked up what could so easily have been a two dimensional villain and created a delightfully malevolent creature able to deliver some *very* tough lines with a chilling relish.
I adore the Paternoster Gang. Watching the evolution and continuation of the relationship between Vastra and Jenny is amazingly touching, and Strax, though relied upon slightly to much for comic effect, could become a truly great character. They deserve their own spin off series.
And by gum I liked the aftermath of the Battle of Trenzalore. It looked like a world of graves. Utterly harrowing, and something I can believe the Doctor wanting to avoid seeing at all costs.
Ignoring the usual Who issue of never letting any kind of scientific logic getting in the way of a good story...
Strax got a tiny bit grating. He's good, but no need for some of those lines during times of high stress.
I don't care enough about Clara yet to be bothered by her sacrifice.
It didn't feel like an episode in it's own right. Not even a 'part one'. The whole thing felt like an intro scene for the 50th anniversary. Not a bad thing in itself, but as that's not for another half a year I feel all empty inside!