Looks excellent, you obviously invested a lot of time into this project.

The only thing I would do at this point, as I'm sure you'll continue to tweak this to no ends...would be to beef up that occlusion pass (if you have one....) I'm assuming this was rendered in mental ray. It would make a world of a difference. The shaders (on the engine specifically) are a little too clean.

Sometimes I'll cheat and render an occlusion pass with a low sampling setting just to make things look a little grungy, provided there are no stellar closeups.

Good job, keep it up.