Thoughts, feelings and lots of spoilers.
I am falling more in love with Capaldi's Doctor the more I watch him. He's grouchy, cunning, needy, bonkers, quiet, scary, dismissive and, weirdly, curious. Especially in the presence of an apparently "good" Dalek. This episode was quite dark which allowed him to really go outside of the flippy hands, goofy mannerisms of his immediate predecessors and give us more of William Hartnell's style of Doctor. A little grouchy, a little worn around the edges and much less silly.
The episode takes us inside of a Dalek, Fantastic Voyage-style. The Doctor, Clara and a few soldiers get miniaturized and are on a mission to heal a broken Dalek from the inside. Lessons are learned along the way. I liked how balanced this episode was. There were space battles and Dalek invasions but there were lots of quiet moments, some excellent acting and character development.
I went back and watched all the episodes from last season and I've realized that I don't hate Clara. I think seeing all her episodes strung together, one right after the other, made her arc much clearer to me and she's definitely a fully realized character. What I didn't like about her season was that she was another Companion who was "Special". Her companion wasn't our eyes and ears into the Doctor's life but she was a mystery the Doctor was trying to solve. Personally, I prefer companions who are normal folks being dragged into the Doctor's zany worlds.
Clara now is just Clara. She's not a mystery wrapped in an enigma. She's a teacher working at the same school where the original Companion, Barbara, taught. She has a normal life outside of the Doctor. She reacts and feels and gets angry. She gets scared. She's brave and adventurous. The Doctor got a well-deserved slap from her. I actually like her now that Moffat has shown her being more than Quippy Pixie Souffle Girl. I'm hoping this keeps up throughout the season.
I love Danny Pink already. He's got a lot going on under the surface and that surface is mighty fine. He appears to be a soldier who might have killed a civilian and is feeling immense guilt about that. I'm curious about where his character is going. It seems clear they are going to hook him up with Clara. They have adorable chemistry.
Overall I really enjoyed this episode. Danny Pink had a good introduction that didn't feel rushed or flippant. Clara got some character stuff that's she's building on from episode one. The Doctor got tons more character development. And we got to see them get miniaturized!