Pretty good episode, and aside from "Flatline," already much better than last season (except the fact that Clara is still Earthbound).
I loved the eeriness of the opening and the imagery of eyed-hands reaching out of the mud. That being said, and I knew it was coming thanks to spoilers, I didn't like the premise of The Doctor finding Davros by accident, leaving him and then returning only to say he'll kill him. The whole "will he, won't he" idea has already been explored years ago (as referenced directly in this episode) and was done far more effectively.
Missy is back, which wasn't so bad and I enjoyed the banter she had with both Clara and The Doctor, but I otherwise found her underutilized. Some great callbacks to previous episode and maybe even the audios (and at least I, Davros wasn't dismissed out of hand as I feared!). Still, it lacked something. Don't know what.
Still an enjoyable episode, but missing something.