I liked Children of Earth well enough, though I'm kinda iffy on whether it's part of my headcanon of the Torchwood storyline or something I'm keeping separate in my mind. On principle, I like the kind of plot they used there, I just hated what it did to Jack's character.

Rewatching the early episodes knowing what one knows now about Jack's character would be an interesting experiment. I believe I rewatched some episodes during a rerun, but I'm not sure.