Wooo hooo, been surprised a couple times.
1) Once on business (without family) I was able to rent a BRAND NEW convertible that was sitting on the aisle. It had like 200 miles on it. They also had some new Beetles.
2) Again on business, arrived late and the aisle was EMPTY. Employee told me to go to the aisle that matched the reservation (intermediate or full size) and pick one from there. It was just me, so it was ok.
3) Once, with the family, we arrived very late to find the emerald aisle almost empty again. The only car there was an intermediate, and it was locked. I went and found an employee (took me like 15 minutes) and they said just take whatever car we wanted. We took a van and drove away, not even a blink at the check out booth.
4) In December, the aisle was full of Intermediate and Full size cars. We had booked a full size, so went to go get in and could fit all but one of the suitcases in the car. Went and talked with the guard (we told him we were disappointed that there wasn't a selection of larger cars on the aisle) and he said just go ahead and take an SUV, which we did. Again, not even a blink at the check out booth. We did sweat for a little bit though when they all wouldn't fit...
All in all, the only problem I really had was finding people to help me if I had a problem. The have a little booth for an attendant, but nobody is ever in there. Employees just seem to be non-existent in the rental area. Remember though, <b>they don't guarantee anything more than what you have booked.</b> I've been lucky and had some nice employees let me get a bigger vehicle, but you may not be so lucky.