(Though it was bloody great to see him, and I'm stoked at the prospect of more.)
To me, the neatest thing in this episode was that the first moment we saw Ruth, she was looking at herself in a hexagonal mirror. Even at the time, I thought "Ooh, nice - this character will clearly have some special connection with the Doctor and probably end up on the TARDIS by the end of the episode." She did indeed, but I didn't begin to guess how. Even the symbolism of the mirror image paid off. I love good set design.
Nice that Graham found himself on a hexagonal tiled floor when he woke up on Jack's (stolen) ship, too.
It was just generally a nicely plotted and executed episode. It carried us successfully from an emotional gap between the companions and the Doctor, to them declaring that they knew her, were her family and were ready to help - and her responding to that. It told the small story of Ruth and Lee, and tied it in to bigger and as-yet-unexplained things which I'm excited to know about. (Well, except for the Cybermen. I couldn't care less about the Cybermen.) It made beautiful use of both Gloucester Cathedral and that lighthouse as location settings.
I think I could have done with more coming out of Yaz's role as a policewoman in relation to the Judoon. I felt like lip-service was paid to it, with comments about how she spoke their language and could therefore stall them successfully, but without it really being developed very fully. Still, at least it was there a bit, I guess?
And now we have (sort of? possibly?) had a black female Doctor, without anyone being able to make a big whiny online fuss about it in advance. Although, I would probably have crossed out the line in the script in which 'our' Doctor said rather crushingly, almost sneeringly, to her "I've never been anything like you". Nominally, this was then glossed as being a comment about her shirt, but it did come with the spectre of racist overtones, lurking behind that 'thing' in 'anything'.
I am definitely pleased to see her, and I really like how Hartnell-ish the 'Ruth' Doctor is coming across as so far. My guess is that that's deliberate characterisation, and she is going to prove to be from an early phase in 'our' Doctor's life, her memory of which has been wiped by the Time Lords in relation to whatever lie or secret the Master was on about in the first episode. But oh boy, I hope the Ruth-Doctor doesn't end up going down the line of Jasmine in Angel. That's all.