Bob, we may have to add the 2007 models (at least) as well.

I have three 2007 models currently used as company vehicles. One that I had bought in the October 2006 for my wife (later became the third company Prius) was very susceptible to slow speed climbing of our driveway. She experience the phenomenon in two separate occasions even with Michelin X-Ice winter tires on.

The other two were bought in November 2006 and also have evidenced almost similar behaviors when climbing the parkade ramps, especially when the ice is packed on the surface. None of the events were heart stopping but if the car briefly stops on the incline, getting it to move again requires some care. My guess from talking to other Prius owners in my area is that the 2007 is still less vulnerable to Trac issues than the earlier models.

Cheers;

MSantos