Haven't driven since 95, but am seriously considering it again this summer. Have new suv, uncertain usa situations, save money & economize, etc.... Makes a lot of sense to have your own car in the event you might want to return home early? We were at wdw 9/11.
Anyway, we always go down Il 57 its VERY quiet for us from here, you probably save a good 3 to 4 hours on us! then we move into kentucky and merge into the 65 / 75 rat pack going straight to florida. I do remember, you do not want to get to atlanta at a rush hour time, be it the city or the turnabout. We stopped just outside of it in a small city (can't think of name dalton?) and woke about 3am, decided to get up and GO! we went straight through and was at wdw checking in about 9am! (although tired, very used to swing shifts) took a nap and were up in no time. Good thing GF had our room ready.
Also remember alot of congestion and slow going in: chattanooga, nashville, If we go through indiana 80 to 65 you also have indianapolosis, & louisville.
Total time from Joliet usually 24 hr's driving & keep in mind alot of the southern states have much higher speed limits on the highways.
You have to keep reading the signs it seemed to change frequently, Illiniois is the slowiest of them all.
Good luck, and Happy motoring!
MKY