This is an excellent slice of classic Who. The Ice Warriors make a suitably sinister first appearance that is good enough to make them a returning monster. The sonic guns are as frightful as the Daleks ray guns; and their voices (particularly the laughing hiss) are as imitable as the Daleks too. Patrick Troughton is still at the height of his powers as the Charlie Chaplin-esque comic genius. (A genius barely disguised by his trampish appearance and foolish behaviour.) Victoria makes a great companion as the prudish but Science-savvy Victorian girl, and Jamie is, as always, the lovable truculent Scott.
The plot is interesting and Science-heavy. Although whoever came up with the notion that removing plants would somehow radically reduce atmospheric levels of CO2 needs to go back to school! However, that is really my only criticism of the story. I won't discuss it further for the benefit of anyone who hasn't seen it. There is also a great character-driven and nuanced subplot exploring issues around Science v Nature, man v machine and obedience v freedom.
Finally, the animation may not be ground-breaking but it is very watchable. In particular the main characters are well drawn. It fulfills its purpose of making the story feel complete in a way that linking narration and audio-only episodes could never hope to achieve. In addition, since this is a six-parter, you still get four live action episodes for your money. So really I think people should stop complaining about this aspect of the DVD! It is thanks to the animation that I have for the first time sat through and enjoyed this adventure (and I am a long-time fan of the show).