Got the lens 2nd hand from Japan. Came in mint condition, with original case, unused strap and lens cap.
I read several reviews (not many can be found), and came to the conclusion - confirmed when I received the lens - that this would be a great value for money.
The build quality is great (all metal). The focus is better than I feared when reading reviews. It is not usm, but not very noisy and fairly effective. I haven't tried yet in low light conditions though.
The image quality is quite good. However I haven't compared in with the sigma or the canon (haven't got them!). But at least, when I switch from my canon 24-70L to this, I don't feel like I'm on another planet. Maybe a tad soft at 200 2.8. But not a big problem for me as I use 200 2.8 to do portraits and blur the background, ie most of the image save for the subject.
All that for a price 40% less than the Sigma, and 60% less than the canon (non IS)...