The intro was a lot of fun. I loved how Missy explained that it didn't matter - to her or the story - which Doctor was in the precarious situation. Of course, they had to do that so that no one important throughout the episode (or the previous episode) could possibly be actually killed by a Dalek blast. Now or forever, really - if the Doctor has a device which charges off the Dalek blasts and renders them useless, why doesn't he carry it with him always?
I again enjoyed the Master quite a bit, because again, she's showing the intelligence she's always had. And, of course, some of that insanity, too.
The discussion between the Doctor and Davros was fantastic, finally showing some depth to Davros' character and exploring concepts of friends and enemies and good and evil - until Davros asks, "Am I a good man?" I'm sorry, but that call back to Series 8 was a very clumsy parallel to the Doctor, just as bad as the monologue about the dinosaur, the monologue about the robot, and the mirror-finish serving tray in "Deep Breath". It wasn't good then, and it isn't good now. With deft writing, the audience is capable of making the parallels on their own; when you ram it down our throats, it loses all of its meaning and power.
The trap was great, but the resolution was terrible. We are really supposed to believe that the Doctor knew exactly what he was doing all the way? And, unfortunately, the concept of the Dalek graveyard, populated by vaguely sentient Daleks, beneath Skaro was stupid in the first place, and then you find out it was really only created there to be the deus ex machina. Not to mention, didn't we just have an episode in which all of the dead individuals of a species come back to life? Oh wait, no, maybe this was calling back to the piles of discarded Flesh. (I suppose Dalek-Clara brings up "Asylum of the Daleks" - this whole episode is just one big mashup of old ideas.)
Unfortunately, one of the main breaks in the episode for me was the scene where the Doctor is talking to Dalek-Clara, and he stops because, apparently, a Dalek shouldn't be begging for mercy. Of course, we've already seen a Dalek beg for mercy, in "The Big Bang".
RIVER: I'm River Song. Check your records again.
RIVER: Say it again.
RIVER: One more time.
Yes, the Doctor wasn't there, but it does not ring true that the Doctor, the man who knows the Daleks best, would say such a thing when he's seen plenty of Daleks act in unusual ways, many of them during Moffat's tenure. Don't they have continuity people checking this stuff? It really breaks the story when they can't keep their own history straight.
So, bottom line, it was good for a while, broken at the end, okay on average.