Priceline works with the major rental car companies, there is no guarantee who you will end up with until after your bid is accepted and charged. I used priceline last year and again for our trip this coming May to MCO, I paid $155for a 7 day mid size car in May this year and $145 last year with Hertz. I did not have to wait in line, but I did have to use the kiosk to check in and get my car. It was very simple, even using the shuttle to get to Hertz, not a porblem.
Any other questions feel free to PM me.
Good Luck
Lisa