So strangely, Dan and I seem to agree: Russell T Davies seems to have knitted together a TV show that is much greater than the sum of it's prior parts. Furthermore it is quite apparent that he'd be quite happy to move the series past it's small-form BBC Cymru roots to a grander vision with international locations and big guest stars (Bill Pullman! The former Mrs. Clint Eastwood!). After all, he jettisoned all the previous cast except for the two leads, and these characters spent a lot of time distracted and off the procedural trail. I won't be too surprised if the leads next year are Mekhi Phifer's Rex Matheson (quite the sly, TV-sci-fi tip of the hat, that character name) and either Jack Harness or Gwen Cooper.
And yes, I'll agree that John Barrowman is not an especially compelling actor. I was gonna chalk it up to my mistaken idea that he was an English actor being held back by having to do an American accent, but he's basically American-- Scots-born, grew up outside Chicago, he was in an extra in The Untouchables (1987). My wife is terribly perturbed by his hair, which changes drastically from shot to shot.
Honestly, if the premise of the next season is anything like the compelling one of Miracle Day, the whole Torchwood/Doctor Who backstory can be dispensed with.