I got the car I wanted.
I do it this way. First I go to a site like orbitz.com & check using the dates I intend to rent. This will show me which companies are offering the lowest REGULAR rates.
Then, using this info, I go to rentalcodes.com and check rates at some of the lower priced companies which I found through my Orbitz search, but this time using discount codes.
Finally, using the lowest rates found from those searches, I enter a bid on Priceline which is lower than the best rate I found to that point. Be sure to factor in fees and taxes which Priceline tacks on to the final cost when deciding what to bid.
Other than that, I had no isssues, once your bid is accepted, Priceline chooses the company and it works just like any other rental would.
Good luck