The Sound of Drums is a pretty excellent follow-up to the events of Series Three and Utopia specifically. It is great pay-off to the Saxon plot threads. John Simm is pretty strong as the Master, too. The stuff with the "aliens" and such was pretty good set-up even if Last of the Time Lords didn't totally manage a great follow through.

There's some really great elements of production, too. The use of the song The Sound of Drums was great, the Paradox Machine looked awesome, and some of the other CGI stuff is pretty well done given the age of this episode. Some of the acting leaves a bit to be desired in the form of Barrowman and a couple of the guest stars, but overall this is a very strong episode on the whole.