I've done a little bit of longer distance riding on my DR. Dirt tires. It does of course give you vibration at highway speed; that's a big piston slapping up and down there. On the highway I can pull in the clutch and the vibes disappear to the point that I don't know if smooth tires would even make a difference.
In any case, it's not particularly bad.
Out on the long slab at 75 it's very tolerable, for what it is.
On dirt roads and paths, it's very much in it's element.
On a twisty paved mountain road, you feel like nothing can beat you.