The German Blog Docma published the first review of the new Sigma 135mm f/1.8 DG HSM Art lens (tested on Sony a7RII with MC-11 Mount Converter/Lens Adapter). He said the Bokeh is very harmonic and shows no artifacts and it is sharp from edge to edge even at f/1.8 aperture.
Conclusions from Docma: (Translated by Google)
If you prefer people and objects from a distance than to be in the midst of the turmoil, the Sigma 1.8 135mm style will love. Its background softening qualities are (almost) unrivaled, which should be appreciated by fashion photographers, especially if they want to stand out their whole-body models from the background. Technically, the Sigma 1.8 135mm style seems to get along without compromise. Apart from the dimensions, which are not unusual for these focal lengths, for size and weight.
Sigma MC-11 Mount Converter (Sigma EF-Mount to Sony E): $249 at B&H.
Read the full review at Docma.