We were just there a week ago today (Sunday)--not an RV trip this time, but auto and stayed in a B&B in Cumberland Gap, TN.
We only had a limited time there, but made the drive up to the Summit overlook. There are some nice trails--not too long up there. And great views. You can look almost straight down into the town of Cumberland Gap, TN, and see several states.
We were there a year ago on an RV trip and stayed in the National Park campground. Very nice, just no water hookup.