500 miles so far
I installed K60s front and rear after nearly 11,000 miles on the original tires. My first impression is that the Heidenaus were much squirmier on the pavement but I got used to them after a few hundred miles. (Dry pavement, above freezing temps).
I tested them a bit (25psi front/rear) in off road conditions (steep hills, grass, dirt) and am pretty impressed. Even with the center strip on the rear (150 width), they powered up a pretty long and steep grassy hill, spinning but still providing traction.
I got them for a planned trip to Big Bend National Park in TX this summer, will see how they perform there.