I've used it before as well. They only use the national chains, so you don't have to worry about getting Krap-E Rent-a-car (who takes your res for an SUV, but gives you a compact for you to attempt stuffing 500 pillows/blankets in and driving with them touching your ears.....THAT was a fun day!)
The only possible hitch you might have is in terminal/long shuttle ride as space can be tight at some airports, but I've never had any trouble w/ Priceline.
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