The K75 will eat up miles more smoothly & effortlessly than one can comfortably manage on an R65, though they are more complex/less user-friendly to service, they are generally pretty reliable, from all that I've seen/heard from friends who've owned them. They do sound like a turbine going down the road though. With the counterbalancer system in the triple, it is definitely smoother and not buzzy like the K100 bikes I've ridden. The valves on my cousin's K100 don't need to be touched until 20K miles or so wind up on the odometer. The fuel injection is mostly a leave it alone affair, with occasional throttle body synch, and change the oil/lube the splines (yes, even they have clutch splines to service and getting to them is more effort, IMHO.
The only achilles' heel on the K75 that I am aware of is the rear shock - for some reason I know of several people who have had the rear shock break on them, and the bike definitely wasn't overloaded at the time. Putting a new shock on and all is well. It seemed to have happened with a couple different brands of shock, so maybe I just know some unlucky people.
Otherwise, I'd agree that the K75 is probably the nicer of the K-bike "bricks", and, just like the R65, it is often the under-appreciated/ridiculed one for no valid reason.