Bad, very very bad in OKC.
Airport is working on the parking lot and they have turned it into a giant mess. Used to be you could walk outside and it was a short walk to where you would pick up the cars. Now you have to go downstairs and through the tunnel past where they used to have the cars and through a construction area to the "temporary" rental car area, and it is confusing. Parking garage is a terrible mess, as you will see next month.
Still no aisle, you have to go to the kiosk and they will give you your keys, which defeats the whole purpose of the Aisle where you select the car instead of the counter person. The National car selection is very very slim, although there is always a very nice car parked in the VIP spot that I have never been able to rent, nor have I seen anyone drive off with it.
I've given up on on National in OKC, switched to Avis/Budget, as I've found they have much nicer, newer and better equipped cars for less money, and they have active XM radio. I was getting better service before I got status from Avis/Budget than as an EE with National. When you return your car, there are a bunch of people there, but they are Enterprise employees and can't check you in, you have to wait for the National person, or they have to go hunt down the scanner which is always a time consuming operation, much like the checkout. At least with Avis/Budget the same person can check in either car.
I've been told by the car rental employees that in two years they plan to build an off premise car rental center a couple of miles from the airport, so it sounds like a bad situation will soon get worse.
I'm still a National customer, just not when I rent at OKC.