First thing's first. If you live in the city especially a rather large city, you have to get out of town to get to the good stuff. That means, interstate highway.
I use to have a K75S. It would do fine on the highway, but it would get buzzy at around 75-80 MPH. The F800GS has a 6th gear. I found that 80 MPH was it's sweet spot. That's a little slower than my R1150GS which likes to be at 85-90 MPH. That doesn't mean that it won't go 90. When I rolled on the throttle to pass, it got there really quick. I didn't even need to downshift!
Before I even got on the bike, I was really concerned that the F800GS would have the highway characteristics of a couple former bikes I had owned previously that had 21" front wheels. Both the KLR and an LC4 had an unsettling wobble at speed that I really did not like. This didn't happen on the F800GS. As a matter of fact. This bike has that best feel for the road than any telescopic forked bike I have ever ridden. I really am spoiled with the R1150GS's paralever suspension. The F800GS takes a little more effort at the bar to steer than the 1150GS but I got use to it in short order.