After watching this serial it was interesting to read that it is generally considered amongst the great Doctor Who stories. I was glad to be able to watch the serial without this pressure, because maybe I would have been disappointed, or surprised, because personally so far I confess it would be one of the serials that leaps to mind as being a favorite so far. That said, it is still and enjoyable and engaging one.
Part of this is it being a blend of content, from Victorian England through to mysticism and more normal sci-fi elements. The story has plenty of colorful characters too, while the horror elements are mostly nicely done. It probably didn't need 6 episodes to tell the tale, but at the same time there is just about enough going on to prevent it feeling slow and padded (mostly). The sense of humor remains too, and Baker leads on this well. Jameson is enjoyable as Leela – out of her skimpies in this one, but still manages to get into soaking wet clothes for a bit. That element aside, she is a strong character – not the most nuanced perhaps, but not just screaming waiting for help. In support Benjamin, Baxter, Bennett, Spice and even Roy are good value – albeit the latter being an issue to watch with modern eyes.
The element of racism in his character (or rather caricature) is unavoidable; not just in the delivery, but also in the writing – normally the Doctor is all about the oppressed minorities when the serial has that as its moral message on a far-away world. Here though he is not fussed by anyone's insensitiveness. To be fair, although it is hard not to feel uncomfortable with the portrayal of the Chinese, I think it is more that all the support are caricatures – cockney, posh old English colonist, etc, albeit that the Chinese is along racial lines. The other weakness is smaller, which is the giant rat; as an idea it is good and it is pretty intimidating, but the visual reality is less impressive when it interacts with people.
I'll stay out of the debate about the 'classicness' of this serial, but it was certainly enjoyable for a variety of reasons.