Pros: The staff tried to make the best of a bad situation (apparently several cars were not returned on time the day I and several others showed up for pickup). The staff gave me a discount for my inconvenience.
Cons: The intermediate-size car I reserved wasn't available at pickup; after about 1 hour of searching other locations, I left with a van. It was so unwieldy that I exchanged it for a compact at a third Enterprise location half way through my 10-day rental.
I believe the staff really tried to make the best of a bad situation. Suggestions to avoid this in the future: (a) always have at least one extra car of each size handy to compensate for cars that aren't returned on time; (b) increase the penalty for not returning the car on time.