Following the review is a very detailed recap of the episode, including quotes (yes I went overboard again).
Compassion and choices. That's what the premiere of Doctor Who
is really about in the end. Does the Doctor still have compassion; is he a good man? He struggles with these questions throughout the premiere - his leaving of Davros as a boy could very well have made him the monster that he is, yet his change of heart to later save him gives Davros and the Daleks the understanding of mercy.
Davros questions The Doctor towards the end of part two if he could commit genocide - as a choice, not as self-defense but a choice. This is actually a resurgence of a similar choice, as The Doctor faced the same predicament in "Genesis of the Daleks" in the original series. He then, as well as in this episode, chooses the higher road. Though Davros has shown his compassion not to always be a good choice, saying it might kill him in the end.
His compassion is a big part of what makes The Doctor who he is, rather than someone like Missy: he is a good man, whether he accepts the fact or not.