I almost traded my 09 GS on a new 1600GT. Very glad I did not. Test rode a GTL, my legs are much too long and it was very uncomfortable. The GT fits me well, but still not as comfy as the trusty GS, which fits me perfectly. I am 6', with 34' inseam. The windprotection is awesome on the GT, no so much on the GS, even with an aeroflow screen. The GT is very powerful with the associated twitchy (read very touchy) thottle. Both handle very well, the GS more so in my hands. Gas milage is about the same at superslab speeds, I thought the GT would be better. At the end of the day, the GT is a very heavy road bike with wonderful manners, but heaven forbid you should have to turn it around on a narrow, unimproved road- again,it is a very heavy beast. So, I use the GT on long paved highway road trips, and the GS when I will go down more adventuresome paths. Very thankful to have both! Good luck on your decision!
"If the going is getting easier, it is probably because you are going downhill"