Just watched this episode and I was really pleasantly surprised.
Didn’t know this was the first part of a three-part finale and so had just been expecting a filler episode which reintroduced the character of Captain Jack, but damn me was that good stuff even with the paper thin plot.
The plot was really just a shallow backdrop for what was an excellent character piece.
I love the character of Captain Jack Harkness and that the Doctor is both terrified of and attracted to him. Every piece of interaction between the two of them in this episode was brilliant from the bit where Jack talks about the Battle of Canary Wharf and the Doctor reveals that Rose actually survived to their talk when Jack was in the radiation room.
Derek Jacobi was rather bloody good as the tragic Professor Yana and wonderfully sinister Master. It seems so cruel that the almost saintly Professor who was willing to sacrifice himself to save what little remains of the human race would contain that monster.
Wasn’t too sure about John Simm’s version of the Master but then I think that they are trying to strongly establish him as the evil version of the Doctor as he has the same kind of insane exuberance that Tennant’s incarnation of the Doctor has.