My experience was perfect. I arrived the night before and went back to the French sector of Geneva airport to pick up the car. The agent was very kind to present the different options I had, and even though I mentioned I will mainly be in France and did not need the highway sticker required for Switzerland, I was given a car which already had one just in case. I was also upgraded to an automatic car while my reservation was for manual with the automatic being preffered based on availability.
The way out of the rental car station leads to just north of the runway on the French side of the border, and the same way back from Geneva through Route de Ferney into France for drop off turning left immediently after the French border checkpoint into the airport service road Route de Douaniere that winds its way back to the airport terminal