Well, I have it
I didn't find the screwdrive particularly noisy. Not noisier than my other screwdriven lenses. Of course, the Sigma has internal focusing so it does not have to focus large chunks of glass.
Handholdable? Yes, for a few seconds. Or longer if you have powerful biceps (I haven't). Actually this summer I have walked around with the lens (mostly carrying it while holding the tripod collar) for two hours and after that I definitely was exhausted. But it can be done... It's more transportable than the FA* 600/4.
Sharp? Hell yes, even wide open. But that's to be expected from a lens of this caliber.
Have a look at the Sigma lens review section in this forum. There you'll find a picture of my Sigma mounted to the K20D.