Well I'm not ashamed to say I honestly enjoyed that. After last week's lukewarm Bond pastiche Chibnall reverts to writing actual Doctor Who, and while it's by no means great Who, at this point I'll happily settle for "recognizable as".
Things of note: most RTD and Moffat-penned two parters led with incredible episodes and fell apart completely in the second half, to the point where I can't easily remember one that didn't, which means that Spyfall scores significant points from me for not falling into that trap. Additionally I'm going to say it: I much prefer CC's conception of history to either Davies' or Moffat's. Where previously the past was a very silly place only really good for Blackadder-style sendup, Chibnall treats it with some respect, and the assemblage of an all-lady historical superteam of The Doctor, Ada Lovelace and Noor Inayat Khan is rather pleasing. (On the minus side, it does further sideline the actual companions this week, who have little to do apart from some slapstick nonsense involving Graham's laser shoes.)
The Doctor was actually Doctorish at various points this episode and I liked the fact that sometimes she too forgets she is no longer a man - the body you find yourself in doesn't and shouldn't matter, and shame on those who still can't get past it. Sacha Dhawan's Master is a bit young and good-looking for my tastes (see also David Tennant) but he can turn on a convincing level of thuggish brutality which I reckon I prefer to the John Simm zaniness. The Master chasing the Doctor about through history and finding himself landed in ever more disastrous predicaments of his own making recalled the Davison era in an entirely acceptable way.
So yes I'd probably rate this a solid, baseline 7/10. It's still a fair bit more lightweight than I'd ideally like the show to be, but it's no CBBC-level offering like The Sarah Jane Adventures either (and the "fans" seemed quite happy to tolerate that). I'm now optimistic that Chibnall could amaze us all and write an 8 one day. Go on Chris! You can do it!