Just made this trip last week.
As everyone else has said, the trip is a moderately easy trip. The mountain passes are well planned, and there are only a handful of really steep grades. When you are going up a steep grade, the highway adds an additional lane for slower traffic. Going down is well marked. I usually don't use my gas pedal going down, just let my car and gravity do the work. The fog is really bad at night, and VA has a lot of deer that eat along side the road between midnight and 6am. A daytime trip is the best.
Gas prices: You'll get the best price if you top off your tank while in Ohio, and then fill up again in Wytheville, VA. Absolutely do not leave Charleston, WV with less than a half tank of gas.