Oh, where do you begin? Let's begin at the end. The Doctor can't give John Smith back to Joan. He can't make amends by taking her away as his companion; he can't even understand, until he's told, why it's wrong of him to offer. What he can do is take horrific, mythic and highly apt revenge against the Family on her behalf and his. Looks like the Doctor's taken it all a bit more to heart than he might let on.
That's just got to be 10 out of 10. And the great thing about Human Nature/Family of Blood is that it tells us everything we need to know about the Doctor by showing us everything he's not (and everything he can't have, of course). As with last week, the adaptation from book to TV show is predominantly in the TV show's favour, especially with the fantastic flash-forwards scene. Interesting to see aspects of the novel's ending stuck onto the end of the episode - I kind of felt that it had already ended when the TARDIS vanished, and that perhaps there was one ending too many in there, but still nice to see it. It's still more beautiful in the novel, but then the rest of the story is that bit more beautiful in the episode.
The only way that could have been better is if Old John Smith on his deathbed had croaked out "Rosebud". I jest, of course.