You never know what you will find in ATL, it can be like a living, breathing beast from the depths of hell, and sometimes it's not to bad. I've lived in the area for 10 years now, and hate going into the city. You can't predict whether you are better with 285, or going straight through, one wreck an it changes.
A GPS with traffic data makes things much better, but it can change quickly. Just fuel up and go to the bathroom before you hit town and be patient. I used to get so frustrated with the traffic. Now when we are stopped, I just remind myself that atleast we aren't in the wreck that is causing the slow down.