I’m digging the noir style here.  It works well with this episode arc since the drama is mostly psychological instead of centered around a villain.

Interestingly, this episode marks the first mention of the TARDIS as a possibly sentient entity instead of just a machine.  I’m not sure how big of a role this concept will play in the classic series, but it’s been important from time to time in the new series (like the Bad Wolf storyline with the Ninth Doctor and “The Doctor’s Wife” with the Eleventh).

Barbara: “I went to Skaro and all I got was these pants (and a massive dose of radiation poisoning).”