I had a reservation and wanted to change it, problem was all the cars were booked. I called up avis and they said my car will be held for 15 hours so it's no big deal. I goto the location and ask this in person and again, no problem, just show up.
So I show up 4 hours after my reservation and the first thing they say is "your car is gone". I mentioned the above and the gave me a minivan and charged me an extra $10/day which they didn't communicate well.
After returning on time with a full gas tank they wouldn't reconsider the $10/day charge. Told me the manager would call me - he never did.
When you pickup the car it's very confusing and difficult due to the system they have down in the basement. It's not signed and far from intuitive.
Also, they charge a $10 parking or location fee.