Well, it took nine weeks to get here (special order from Japan by Pentax Canada, who don't even list the lens anywhere anymore), but it finally arrived last monday !
It is light yet seems solidly built, and I really like how it looks with its hood mounted on my K10D. The focusing ring is unusual but feels nice. One strange thing is that I can turn it even if the camera in set to AF-S (even though it is clearly connected to the AF motor).
I haven't had time to play with it all that much yet, but here are the obligatory first few pics, all are 10MP *** JPEG straight from the camera (resized to 800x536 but otherwise unmodified):
f/2.0, 1/20s, ISO 800
f/2.0, 1/2500s, ISO 100
f/3.5, 1/1600s, ISO 100