Here is some info.
My 6k sustained a fall to concrete as I was stepping out of a pickup truck. Which is certain to be at the upper extreme of the published 3 ft level. I was worried at first because both the SD and CF cards were knocked out of it, as was the flip screen cover knocked off. The only permanent damage seems to have been the plastic case surrounding the socket for the stylus, which was dented. However, once I got the stylus out, I shaved away the caved in section and it works fine again.
I just thought I'd post this little testimonial pertaining to the durability of the Z. :)