I have had the same experiences as most people with slight movement due to wind, passing trucks, etc, but the biggest factor for me has been the quality of the road. The car was fine up to 80 on our ride home from Jacksonville, and my northbound interstate ride to work is no problem, but I have found an alternate route home because of the surface of the southbound lane. It's just too wavy and trenched to drive with the smart without feeling like I'm weaving. Nothing that would have kept me from buying the car, but I might be having second thoughts if all of the roads around here were that bad.