i've rented from fox a number of times, most recently at sjc over new years. while i'd definitely do so again in cases with extreme price differences, i have to admit that i couldn't help but thinking how much fox resembles the ficticious competitor in the current hertz commercials: incredibly slow service, dinged up cars, and a general feeling that it would be best not to run into trouble of any kind. apparently the guy in front of me in line was a returner who had gotten into a minor accident, and he was basically told to forget about making the 5p flight, let alone the 4p that he was booked on.
i've been sticking with budget and national of late. both are pretty cheap and are great in the service department. plus, for the most part, budget doesn't charge drop fees.