I came from a GL1800 Gold Wing, so I can tell you about smooth. However, I don't find the 9er to be rough. It's smooth as silk up to about 60 or 65 mph, then it sounds more buzzy than it actually is. I don't find it bothersome at all, and I've never experienced any numbness setting in at any speed. Maybe my face due to the continuous wide grin when riding it, but not my feet or hands. And yeah, +1 on the aftermarket seat. I had a Russell made for my bike and it is super comfy. A lot of folks like the Mustang. It just didn't work well for me.
"Don't sweat the small stuff---it's all small stuff"
'09 650 VStrom