ATL is always difficult with afternoon storms in the summer. I'm always thankful I have family in ATL that I visit all the time. So when I'm visiting family in South Carolina and there's a chance I will get stuck in ATL I just call them up and they drive down.
The worst I've experienced in ATL was on my flight SAN-ATL. It was a late flight into ATL since I left after my last class that day. We landed around 8:15pm and pretty much stopped after vacating the runway. We found out there had been a 4 hour ground stop during our flight and the whole thing was one giant cluster F%&$. By the time we got to a gate it was around 3:30am.... that was a LOOOOOOOONNNGGGG night.