I honestly can't understand all the bad ratings. Maybe I have been lucky. I will say that my experience with fox is as a local and not a tourist.
I have used Fox twice and both experiences were as pleasant as renting a car can be. My reservation is always kept and my requested car available. Their agents are friendly and not too pushy. ( I hate overly salesy rental agents).
Their prices are probably lowest in Vegas because their facilities are away from McCarran.
I would always expect a wait in line at a car rental place, especially at certain peak hours. I was in line this last Sunday at 3pm. Not prime time but there were about 20 people in line. It only took about 20 minutes for me to get to the front, much less than I expected.
Its never enjoyable renting a car but if you have to Fox isn't half bad.