It's nice, but has the potential to be kick-ass! Some quick suggestions:
-there could be more water drops - maybe made using a subtle bump map, or some other method - more small, irregular drops all over the car
-some post effect like bloom/glare could add more "cinematic" look to it
-the drops sometimes look more like dust/dirt, I think they should be darker
-how about DOF?
-there is some flickering visible on the tiny objects such as the drops - I think it needs more AA to get softer, you could try lowering GIvsAA value to 8-4 (but definitely not less than that) and rendering a few more passes
Other than that, awesome project!