My wife has a '13 G650. It kinda vibrates in the seat, which I think is a low seat. The bars don't seem to vibrate very much at all. Then again I was going 50-70mph. Of course, it's in a particular rpm range (maybe 4k). It could just be this bike. Others don't report any issues.
This has been my experience with my '09 G650GS too, the seat seems to have the most vibration. Right before I purchased it, a new seat was installed, so I think it will take a little time to break in. The handlebars and pegs are relatively vibration free. I did notice that some of my vibration comes from my current tires too, as I have coasted the bike down a long hill at decent speed. I too will be using the Thumper to go from Key West, FL to Deadhorse, AK next year, but taking a little more time.