My husband reserved a car with Fox because of its super low rate. In my opinion, it is not worth it.
It took us one and one-half hours to get out of the place with an acceptable car. We arrived on a Sunday and the line to pick up was about 30 deep. Very slow service. Even though we reserved an intermediate car, they assigned us an SUVish vehicle, which we did not want since we were planning to shop and did not want shopping bags exposed in the back. The agent brought us another vehicle and we went through the inspection process (there were MANY dings, etc.) and went to the exit. The agent there said there was a hold on that vehicle and we couldn't take it. So we had to drive back in and wait more for them to find us another vehicle.
Even though we had said we would bring the car back with a full tank of gas, they put an approximately $50 car on the contract that we had to deal with when we dropped the vehicle.
Yes, you do have to take an additional shuttle from the car rental center at McCarran, but that wasn't a problem. In a town where customer service usually exceeds that anywhere else in the US, we found the personnel to be slow and ineffective.