I've used it for both, about 1 year ago. The process was very very smooth..... my car came back clean, with a full tank of fuel. Renting was good too... they did all the proper checks, the owner met me at the car on time, and I was out of there within a few minutes.
Would I use them again? Sure, definitely. But I don't have a car at the moment to rent out... and haven't needed a car for awhile either.