I saw the company testing this on a TV science show about a month ago and it seemed interesting ... basically they are taking the technology behind golf balls and trying to apply it to the areodynamics of a car. The skin wasn't smooth. It had dimples (very small) all over the place to chnage how the air travels around the car
They tested it on a 911 first with the skin and then without. The lap times and MPG were significantly lower, but I didn't fully trust the results because they weren't using an independant driver.
I wasn't fully convinced, but it did sound very interesting ... I hope it does work. It would be a major breakthrough