The GT is a lovely bike. It does however have one weak point, which I understand is also shared with the K1600.
The radiator...
Located low in the frame it picks up dirt from the front wheel, and after a while the lower part clogs up, in spite og the tiny center shield.
At normal driving you do not notice it, but climbing a mountain pass behind a camper or queuing in the city, it will overheat.
The thing is, due to the slanted engine, the electrical cooling fan has to be positioned at the lower end of the radiator. When the radiator clogs up after a year or three, the fan will not be able to handle the slow pace.
I've had two of them, and I solved the issue by removing the radiator and flush it with a powerwasher (at reduced pressure). Doing this every 24 months kept the bike from overheating. Also, invest in a vacuum fill kit used to refil the system.
Some people claim you don't need it. Well, the chances are that there will be airpockets in the headn refilling, and this spot heat may wrap the head. A much more costly affair than buing a vacuum-fill kit...