I personally love automotive photography. Here are a few examples of shots I've taken. I shoot with a Nikon D300 and use various lenses depending on the application. I would say most of the images I'm posting as examples I'm using a Sigma 24-70 mm f/2.8 lens. I'm pretty happy with the Sigma products and have no complaints yet. For post processing work, I import my images into Aperture 2.1. Here I'm able to control color, white balance, exposure, etc. I also use Viveza to control light, shadows, contrast etc. Here are a few examples.
Audi R8 at NYC showroom. Photo taken outside from window. They were closed because it was Sunday.
Audi R8 Headlights. Same day.
Ferrari 360 Modena. I definitely know I used my Sigma 24-70 here.
My Car. Again taken with the Sigma 24-70 mm f/2.8. By playing with the contrast, sometimes you can get more detail. Your background and scenery will be a big part of your image as well.
I think with the combination of a good camera and post processing, you can do a lot. I probably wouldn't play with the focus too much to make things over blurry because it sometimes doesn't look natural. Most of the time I'll control my aperture to get the proper effect so I don't need to electronically modify the image. Often times when playing with software to make the image look like the background is blurry, the fine edge between the actual object and the background isn't clearly defined. By using a correct aperture, you're guaranteed that the image will have the correct depth of field look.