I used to live in Winchester, VA and have ridden down I81 many times to Deals Gap. Recently I rode I81 as part of my first SS1K effort from Southern Maryland to Little Rock, AR. In general, I81 is fast moving. There is a fair share of shipping trucks mixed with local and holiday car traffic. Because of the truckers, I haven't experienced a high percentage of left-lane hangers lasting long. If the weather is rainy, you can experience an occasional hazy/foggy situation in the lower dips, but usually conditions have to be just right for that to happen. In general, be cautious, but I don't consider I81 dangerous. Hope that helps.
81 is an easy moving interstate, as mentioned above there is a fair amount of trucks on it. My suggestion is to NOT exceed the speed limit in VA as the laws towards that are highly strict in that state
+1 @413Sean I travel 81 often, and I find it a good driving road with signs telling me that it is considered reckless driving above 80MPH. Traffic moves at a "relax" constant speed. When I get to PA, CT, MA my concentration increases.
Yes I run that stretch of 84 from ma, ct, , to 81 from scranton pa to bristol tn a couple times a year usually on various iba rides and I have a good friend in Andrew's NC, i branch off of 81 on to 26 towards Asheville when I him visit in april and oct on my way to barber vintage fest. My other suggestion is watch out for the "safety corridors" along 81 in VA as the speed limit drops to 60mph and well they keep close tabs on that