The Sigma 120-300mm f/2.8 DG OS HSM Lens is the first "Sports" model from Sigma's Global Vision lineup to hit the streets. The review page now has links to image quality, flare, vignetting and distortion test results along with product images and lens specs/measurements.
I'm still trying to find out exactly what is new with this lens, but the image quality of the lens in my hands right now is impressive – noticeably better than my previous version lens (comparison).