Keyshot is an excellent program, I haven't had time to experiment with it myself, but it looks really simple to use.

I do think you have lighting and surfacing issues though. The car is stronger lit that the environment and some of the shaders are picking up crisp reflections which look unrealistic. The car's slightly too reflective imo, so you're killing alot of the realism in it by making some of the dark blacks completely gone. As a car artist within the games industry I suggest baking out an AO pass, and using that to maintain your natural darkness. A reflection fall off on your shader should also be looked at, cars don't have perfect reflection like an HDR reflection ball. Reflections should be nice and clean, not stretched.

Also watch your geometry, some of it is quite wavey which causes the distortion you will see in your reflections, another reason why you may want to dial down the reflection. Keep it up, you've progressed well from looking at your other works.

That's really awesome. The lighting, textures, and shading are really nice. The only nitpicky things I see are that the headlights are too reflective (given that their behind a glass cover) and the reflections on the door are a little wonky. What I think happened is that you have enough polygons for a smooth surface (Blender subsurf FTW) when it is rendered as an object, but the reflections (which have a higher sensitivity to differences in curvature) need more polygons to look smooth.

Perhaps this is crass, but just as a learning endeavor, could you possibly send me the .blend file? I have no intention of using your stuff explicitly, but I want to see the structure and design.

I actually thought that this is just a photo showing your fav car.. before reading the description.. :O

Very nice dude. I wonder, have you ever heard of a "Citroen GT?" Only a few were every made. It was concept car that was made only for a game on the Playstation 3 called Gran Turismo 5. You should check out that car and probably consider making one? Just a suggestion, but your work is great keep it up :D