Today I managed to test out my Sigma 10-20mm f4-5.6 ex hsm. I'm loving it so far!
Here are a couple of points that I can say about it:
Build quality is pretty good. It's the usual Sigma EX build with the matted finish.
The focus ring and the zoom ring are not bad either, it feels tight and it won't change positions accidentally.
It includes the hood and a bag.
Features an HSM motor for quick focusing...full time manual override also supported.
Image quality is pretty decent. Corners are a bit soft...UWA lenses are notorious for that anyway.
Basically, you need to post process every shot to eliminate dark corners. Lightroom can do that automatically.
Center is pretty sharp, even wide open.
Chromatic aberrations are pretty minimal. The amount is negligible.
Even using an ordinary uv filter (the thick ones) won't cause vignetting.
All in all a pretty solid performer here!
In a couple of months I'll post more sample shots here.