We left our car at the Renaissance Concourse near the Atlanta airport when we went to Europe for 10 days a few years ago - left it in the lot the day we departed and spent the night at the hotel the day we came home. That was a Good Thing, since the getting home involved a cancelled flight in Paris, which caused us to miss our London-Atlanta flight, which turned into Paris-London-Dulles-Atlanta, which our bags didn't make, which meant filing a lost-luggage report in Dulles in the 45 minutes we had to get out of customs and to the next gate, which was not helped by the fact I sprained my ankle bolting out of the BA lost-luggage office and then realized, when we finally got to Atlanta and it was 20 degrees, that my coat was in my suitcase, which was still in Paris.
The Renaissance was very nice, however, and there is a shuttle bus to and from the airport.