Good to see the Doctor finally having second thoughts about his attitude toward peoples disposability though.
I think this episode showed that he never felt anyone's disposable. The end of the episode was quite significant in that regard. He didn't think that any of the people who died were disposable - or "brushwork" as it was put. It pained him that he couldn't save them. Which is why he's trying to keep the emotional distance we've seen from him.
This episode was a good mix of suspense, silly and fun moments and great character moments. The sentence by the Doctor towards Clara at the end gave me chills. "You were an exceptional Doctor. Goodness had nothing to do with it." I'm intrigued. I suspect we'll get the whole story about the Doctor's doubts of his own goodness by the end of the series.
What did everyone think of Missy's appearance at the end? It was too enigmatic for me to make sense of but I'd be interested to hear your takes on it.