Had an interesting experience with National/Alamo last weekend in West Palm Beach. You check in at the desk inside the airport, but instead of assigning your car there, you just board the shuttle and they drop you off inside the lot at the row corresponding to the size of car that you reserved. The cars already have the keys in them and you just pick the car you want. We had about 10 cars to choose from (probably 4 or 5 different makes). No Priceline discrimination there!