Get Sigma 135mm f/1.8 DG HSM Art at B&H Photo.
Includes images up to full resolution from f/1.8 through f/11. Includes comments on how I think it compares to the Zeiss 135/2 APO-Sonnar.
Together with the Nikon 70-200mm f/2.8E FL ED VR (the zoom that looks like medium format in its rendering), we seem to be in a golden age for DSLR lenses, so much so that I question my Sony mirrorless inclinations, particularly if Nikon delivers a D820 or whatever it will be with higher resolution and at least as good dynamic range and per-pixel quality.
The about $1399 price for the Sigma 135mm f/1.8 is a screaming deal that awaits a higher-resolution Nikon camera body. Were Leica to ship this lens, Leica fanboys would rave about it and it would cost $8000.