I assume you are talking about new cars...I can't speak to that, but I can speak to used cars. This is a fantastic time to be buying! With poor sales right now and gas prices at a 5 year low, this is also a great time to nab a hybrid. The wife and I just picked up our CPO 2006 RX400h in the last two weeks or so and got what I consider to be "stupid-low" pricing on it.
I suspect you would be a popular guy indeed if you showed up as a serious buyer between Christmas and New Year!
Yes, I was thinking about the "new" market.
As for the Xmas-New Year time period, I would image you might have their complete attention being a serious buyer. Alas, my time table is more like Q1 2009.