Here's my XT660R fully loaded.
Did a little Germany trip few weeks ago, 3500km.
Had no problems whatsoever, and thanks to Airhawk which saved my butt
The bike was so heavy with me (115kg) and the stuff on it (tents, sleeping bags, food, etc etc., it got great wheelies because of that :) Also the fuel mileage was affected a bit. Still, it is a great bike to ride.
Btw, don't buy the Yamaha original touring screen. It sucks, a lot of buffeting, it would be better to use original small screen or www.off-the-road.de