I like how this follows up on the dynamic from "Rude Introduction": Jack still being semi-serious about his training, but figuring John's the best one to work out the kinks with, so to speak. And the way that John capitulates to that is both hot and endearing.

And I totally second the comment above about wanting to see them play good cop/bad cop. Maybe not with the Master, though; how come nobody's ever brought Owen into this dynamic?