Don't be confused. Torchwood is not an exciting BBC television program. It is a scheme. A ploy beginning with two seasons of enjoyable drama, minus the ubiquitous "introduce the cast" episode. So you get to know the cast the hard way, by watching teevee a lot. Well, you know what I mean. It's a time commitment, is all.
Then they kill off all your favorite supporting characters in ascending order. Don't let the credits fool you, Jack Harkness and Gwen Cooper are the tag-team main characters--everyone else is just tertiary. Just when you were beginning to figure out how things work, everyone's dead, ending with one half of the best couple in television history. So I can cope with dark and gritty. I can cope with dark and gritty if I get to see Captain Jack Harkness kick ass and take names. You can even keep the bubble gum.
Instead I got Captain Jack Harkness sacrificing his grandson to save all the other children in the world. Perfect. Season 2 resolved his childhood trauma associated with his brother, so now he's run off to presumably guest star in the Doctor Who Christmas Special and repress his grief over his grandson in time to get back to Cardiff and rebuild Torchwood 3 and protect the Earth as usual (assuming the rift isn't fixed by the end of Doctor Who series 4 and move the series somewhere where they won't need to hire so many Welsh actors).
Will I watch season 4? Yes. Will I pretend to resent it. Oh, yes. Oh, yes, will I pretend to resent it.