Sigma DP2 Quattro shows impressive performance compared to the Sony A7r and Leica S medium format!
Lesnumeriques (google translation here) compared the new Sigma DP2 Quattro quality against the Sony A7r and Leica S2. As you can see from the High Resolution images on their page at ISO 100 the Sigma shows an amazing sharpness and detail. Just imaging if Sigma would make a FF or even MF Foveon sensor!
Some more DP2 Quattro tests:
Try the Sigma dp2 Quattro For a Week Long Test Shoot (ThePhoBlographer).
Sigma dp2 Quattro Full Size Sample Photos (ePhotozine).