Nice interface. A few thoughts:

* There is no way to get back to the home screen. If I want a blank slate I have to manually clear out the fields.

* I can't bookmark searches, send them to friends or search for multiple models at the same time because everything is cookie based. Having my search from my last session come up when I enter http://www.carsabi.com/ is also a bit creepy.

* Clearing the "max price" field is broken. All future searches come back with zero results. Refreshing the page shows "$0" in the field.