Greetings from a potential Prius newbie. I test drove two Prius 2 (base) sedans, and noticed a definite "squirming" on the concrete Interstate. The salesman said it was because of the grooves in the pavement. But I've driven my own cars (2004 Solara and 2007 Rav4), and tested several other cars (Corolla, Hyundai Elantra, Nissan Altima) on the same stretch of road, and none of them squirm. This is a worry, because this particular stretch of road is subject to icing in winter, and it seems like a serious control issue. Has anyone experienced this, and is it a problem during winter? I would like to buy a Prius, but I just don't feel safe in the two I've tested. Thanks!