Bought my Orient Blue '04 K1200GT in November of last year and I must say that this is the best of the K12's so far.
Having had two previous K12RS's ('99 and '02), this latest version of the K12RS has all the same great features of the RS and then some, making it a fantastic value as well.
Let's see, you have the smooth 130hp six speed, twin cam, 16 valve four cylinder of the K12RS so that's good plus now, the GT has a heated seat and grips, as well as cruise control and the electric windshield that is also wider & taller than the RS's. I do not like the Mickey Mouse mirrors on the GT (which were the same ones on the earlier RS's) so I suspect a lot of GT riders will be changing these for the RS's or the R1100S's which are fairing mounted.
The GT also has as standard, the wider rear 5.5" wheel. So overall, it's a great bike.