I had factory cruise on my RT, and I really miss that. In my mind, a Throttlemeister is the only way I'd go short of a Rostra retrofit.
I think the final drive design of the C14 is far better than the BMW final drive. Even changing the fluid is far easier. I had to unbolt the muffler, remove the rear wheel and partially dismantle the final drive on the RT to change the oil. On the C14 nothing has to be removed, and it's a piece of cake to do while you're already doing an oil change.
One thing about the Beemer though - I'm not sure if the GT's windshield is the same as the RT's, but it did offer better wind and rain protection than the C14 windshield does.