However, "End of Days" (and "Captain Jack Harkness," the episode that preceded it), presented what I think is the series' first truly mature storyline: the true definition of a starcrossed romance (not gay for the sake of being gay, rather, heartbreaking love story because it's an impossible romance!) juxtaposed with a believable mutiny, climaxing when Owen shoots Jack. The challenging of the team's dynamic (Jack the leader, everyone else subordinate; not to mention the Owen/Ianto struggle the episode prior) was the right way to take the show. Why should Torchwood trust Jack when they don't even know who he is?
I was impressed with the design of the Abbadon, which looked a lot like the creature from "The Satan Pit," but thought it should have been bigger. For the destroyer of the world, it was kind of small. I thought the same of the episode's final showdown with Jack enduring the Abbadon's shadow -- impressed by the obvious solution, but disappointed by the "smallness" of it. No big guns. Just Jack and his surplus of life, which surprisingly, totally made sense.
My final criticism concerns Jack's resurrection. Why would Gwen be able to bring him back to life? What makes her so special? While watching, I thought it would be Ianto, because Jack had brought him back to life with a kiss before. (There is always residual space-time vortex energy! Ianto has got to have some stored somewhere!) Or if not Ianto, I would have been satisfied with a dream sequence in which nearly-dead-Jack sees Rose or "the right kind of doctor" and remembers he's got a ton of life in him. Something.
I'll be more than happy with season two if most of it is up to par with the second half of this season.