I enjoyed it the most of all season 7 eps so far. Lots of action, tension, TARDIS not as invulnerable as usual, LOVED the Library, and we saw the swimming pool. But I was amazed no one
picked up (or has mentioned at least) the other thing Clara saw when she looked into a different room and saw... the Light Chamber from "Tooth and Claw". And yes, that was Seven's umbrealla. And Clara didn't spell reset button on her hand, it was off the hot bomb that the Doctor picked up and burned her hand. And a few people mentioned Logopolis but no one mentioned Castrovalva. And, in conclusion, the voices that we heard at he start included None saying "those doors could stop the hordes of Genghis Khan, and have".
ETA: the lava monsters, I can't see a logical reason for them except as a quick tension-raiser, and they were good as that, but no more.
I'm amazed I picked that stuff up.