I'm with the original poster. I had a gs1100 about a half dozen bikes ago. I had a 950 adv as my last bike. Its not about a weight ratio or other responses in this thread its about the motor. If you ride aggressively the lc8 engine in the high revs is an arm puller and fun as heck. After my love hate relationship with my 950 along and with my serious addicition to buying bikes and fixing them up ($) I have now ended up with another oilhead. I agree, I am very underwhelmed by the power but I knew this going into it and bought this bike specifically for a trip that will involve a ton of paved roads. For this trip I knew a boxer would be the better bike.
Each time I ride the gs I wonder how people compare a boxer to an lc8 engine. HUGE difference. I chalk it up to people defending what they own as being the best which happens all the time (no idea why really but seemes like people do it) and also to riders who aren't agggressive with the throttle to unleash the potential of an lc9 engine...so I can indeed relate to what the OP is feeling