I flew into Concord on an Allegiant flight, and the small size of the airport makes for a quick and easy trip in and out. There is a parking garage of good size if you need to leave your vehicle here, and they have Enterprise, Budget/Avis rental cars available.
We rented a car from enterprise, and the nice part about flying into a small airport is that there isn't a shuttle you need to take to go get your rental... you walk outside and it's around the corner in a lot connected to the terminal.
If you're able to fly into Concord, I highly recommend it as you can avoid the busyness of the Charlotte airport.