DXOMark data is out for the Sigma 85mm, and it both augments and confirms the SLRGear results. It has extremely even performance across the image field, no distortions, low CA.
It's the highest-rated lens on the 5D Mk-II on the DXO site, narrowly edging the Canon 85mm f/1.8. Resolution looks to be between 11MP and 17MP on the 5D Mk-II if one calculates from lppm numbers. This may be near what that camera's AA filter allows anyway, as no other lens has delivered substantially better than that yet (70+ lenses tested).
Reading list is here.