I fly ASA every week, as they are the only game in town. At CSG, the employees are stellar--I'm greeted by name and chitchat about that week's destination. (Although a separate issue, I feel compelled to add that our TSA folks are just as friendly and efficient.) At ATL, it's another world--and not a good one.
In 48 hours last week, ASA left me standed in ATL, stranded in CSG, lost my luggage, and returned it to me in the middle of the night--damaged. As much as I hate the ground commute to ATL, and hate going thru security in ATL, and just generally hate flying out of ATL (flying through is fine), I'm seriously considering it. And if I have to haul my butt to ATL, I will not fly Delta once I'm there. To do so would be rewarding bad behavior.
I've been loyal to DL, but they make it very, very difficult.