I live in FL but just drove up to Michigan and back last week. I also avoid the Atlanta bypass & use the HOV lane but try to make sure we drive through between 11am-3 or after 9 pm. Atlanta traffic is the worst if you get stuck. I try to avoid Friday afternoons/evenings and the day before or last day of a Holiday/Holiday weekend if you can avoid it. This trip I was the only driver so we did it over two days. When we have two drives we often drive straight through.
We hit minor traffic between KY and Knoxville (about a 10 min delay both ways) as the road is down to one lane on each side right now. I have heard that this area can get bad but really we didn't find it too bad. The road was damaged and being rebuilt so I would assume this might take a while so I would expect this delay if your going soon.
The only other issue we had was going south on 75 out of Detroit with all the detours but I would assume being from the area you would know how to avoid that.
If it helps at all we left Houghton Lake, MI area around noon on a Sunday and made it to Florance, KY around 6:30pm. With one stop only for gas. We made it from KY to the Sarasota, FL area in 16 hours the next day. Stopping once for lunch for 1/2 hour,did a drive thru dinner and then just for gas a bathroom breaks.
On the way there we left at 5am. Made it through Atlanta around noon. Timed this great as we zipped right through. Had a quick fastfood lunch. Then only stopped for gas and about a hour for dinner. We made it to Bowling Green, Ohio around 11pm before I had to call it quits. It took us about 3 1/2 hours the next day to get to Sterling Heights, MI.