I'm using this gem on a 5DIV and it just sings.
-- It's slightly sharper than my 135L in the center and much sharper towards than my 135L the edges of the frame
-- Autofocus is vastly improved over my previous experiences with Sigma's 35 Art and 50 Art. In single-shot AF, it focuses just as fast as my 135L, and just as accurately, too. I'm also getting more consistency than with my 135L. Way to go on this front, Sigma, bravo.
-- It's quite heavy, noticeably more so than the 135L. This is a two-edged sword, as it helps to stabilize your whole rig, but hand-holding fatigue sets in more quickly. Lifting weights might help...
-- Build quality leaves nothing to be desired. The mount is rubber-gasketed. Solid as a rock - no creaks, wobble, nothing. First-rate.
-- Bokeh is not as creamy as I had predicted. Perhaps I'm spoiled by the Sony 85mm G-master, which sets the par for me currently, in this regard. The Sigma 135's bokeh isn't bad, not at all, but I feel that the 85GM (and even the 135L) is slightly creamier and less "edgy". (This is very subjective, of course.)