We took I-75 from Charlotte project to the Twin Cities one in MN last year. The oncoming side got stuck in the I-40 mess of traffic accident. It slowed our side down some, but noticed that RV Parks north of Knoxville were few and far between, and kind of on the Yuck side.
We've also taken I-77 up through NC and the WV tolls a couple of years ago on the way to Vienna, WV. They are quick and don't really slow you down. Plus, they don't charge extra for RV's. There was a nice WV Rest Area that had good parking and Burger King among other restaurants. Don't remember anything nice about I-75 except the horse farms.