I have built a car model in direct Solidworks (although most of the ones I have done have been done using sub-D poygon methods). The approach used was to build a spline cage covering the whole side of the car, then creating one large surface. Details like the wheel arches, etc, were cut out afterwards. You can break down a car in to 4 or 5 main surfaces, that are then detailed afterwards.

Here are some renders of the Camaro I did in Solidworks:







There were some really tricky surfacing issues involved in the detail, which I don't think MoI could handle with the current toolset. This model took far longer to produce in Nurbs than it would have done in Sub-D. As it is a conceptual exercise and not engineering detail, nothing was gained by doing it in SW.