I finally got the Kumhos out on some twisties tonight.  There were too many deer out so I took it easy, but I still was able to lean on them in a few spots.  I'm pretty impressed.  They aren't as much of a dropoff from the PZeros as I expected.  Definitely better than the Potenza RE92's the car came with.  Makes me wonder if they will last very long.  But damn, for $70 each mounted & balanced, they rock.