I have made this trip a number of times from NE Ohio before we relocated to Florida, and we're doing the reverse route later this week, from Fl to Oh.
The area that confused my son-in-law on his way from NE Ohio to Florida was on I-77 in Wytheville, VA where I-81 signs are also posted. He missed the turn where I-77 goes off to the right and to the south and he stayed on I-81 for a few miles.
I just checked my Rand McNally TripMaker Software and it has the ability to connect to the Internet and look for construction delays and road congestion along the way.
It shows I-77 lane closures near Stone Creek, Oh.
It shows I-77 lane closures near Newcomerstown, Oh.
It shows I-77 bridge repairs at Marietta, Oh.
It shows I-77 bridge repairs Williamstown, WV.
It shows I-77 bridge work in Charleston, WV until 9/30/02.
It shows I-77 road repairs in Charleston, WV until 7/26/02.
It does not show Charlotte, NC as a congested metro area.
It shows a congested metro area in Colombia, SC.
N of Jacksonville, FL - I-95 five different areas with road widening.
Near Jax airport, I-95 congested metro area near I-295.
In Jax, I-95 Fuller Warren Bridge over the St Johns River - bridge work, elimination of draw bridge, south bound is usually ok, unless accident.
South of Jax - congested metro area where I-295 rejoins I-95 again.
It shows I-95 and Daytona Beach as a congested metro area.
I-4 near Lake Monroe, Fl is the start of congested metro area that goes all the way through Orlando and on into the WDW area.
If you're on an Interstate in Florida and you have a problem and don't have a cell phone, there are Motorist Call Boxes along the side of the roadway, except in metro areas. They are on a post about every mile and you shouldn't have to walk more than 1 mile in either direction to find one.
As another poster stated, Gasoline in Florida is more expensive than Georgia or South Carolina, by about 15 cents per gallon minimum. For planning purposes, it is about 200 miles from the FL / GA state line on I-95 to WDW on I-4.
The state is also changing the exit signs to match the mile markers, but it is a long project, so not very many are done. For example, an exit that I use often is exit 103 and I know that it is near mile marker 353, but the sign doesn't say it yet. The sign says it is the 103rd exit from the south end of I-95, which doesn't make a lot of sense these days, but it's getting better.
hope that helps