I've an 04 Road King myself, At idle, the engine shakes madly in its rubber mounts. Little of that motion gets transmitted to the rest of the bike. Though on occassion, it can shake so hard it makes my eyeballs rattle. It is not an endearing trait to me. But as that's really the only thing I dislike, and it's glass smooth as soon as it's off idle, I'll accept it. Either cut the engine off or rev it slightly if I have to wait a long time. As for ergonomics, Harley has a zillion ways to move your feet, your hands, and your body. In my case, I've got a seat that scoots me forward and down while seated on the bike. My handlebars bring my hands back several inches, raise them a little, and tilt them outwards a bit. With the floorboards, I can put my feet just about anywhere. The brakes are a little bit forward for me, but Harley has a shorter lever that I can install to bring the pedal back a few inches. How is it for comfort? I can ride it all day long without discomfort. No back rest, just sitting upright on the seat.