So I put these Heidenau K-90 on my F650GS a few months ago. My initial impression was that they were really buzzy, but people here said they will smooth out after a while. My verdict after a few thousand miles is that I hate them. They are grippy and all, but they are still way too buzzy. I took a trip down to LA two weeks ago, and my right hand was really numb after the first day and it just got worse over the course of the trip. This has never happened to me on this bike before - I have toured on it extensively, and I have a Kaoko throttle lock I use a lot as I ride, and the only variable that changed was the tires. In fact it took about 10 days after the end of my trip for the feeling to come back to the tips of my fingers.
So....off they go next week and I'm putting Metzeler Tourances back on them.