<GASP>, I love The Aztecs, it's amongst my favorite Hartnells, and certainly my favorite of the Historicals (Though, I recently finally watched Marco Polo Recon, and enjoyed it and I think, I would likely love that Serial if it is ever recovered)
I saw the Aztecs for the first time last year and it blew me away. Didn't shy away from the horror of the time, gave all the leads bar Susan something to get their teeth into, had a palpable sense of threat throughout, had that conversation between the Doctor and Barbara about changing history, and gave the female lead a particularlty strong story, she wasn't just some damsel to be rescued in this (and whilst I haven't seen a whole lot of Hartnell this doesn't seem to be a one off)
is another of the great "Hartnell historicals." All the characters have something to do, whether it's outsmarting Nero, surviving among the gladiators, coping with slavery, browsing the open-air markets... it's one of the best Doctor Who stories, period.
I loved The Aztecs
as well, and I think it's safe to say Susan did have her own part in that - being "re-educated" in how proper Aztec maidens are supposed to behave and memorizing all those rules!