I had the opportunity to rent the new Sigma 85 a couple weeks ago from Lensrentals.com for a week-long catalog shoot I did in Miami. I have to admit, I was blown away by the results. Over the years, I've owned three copies of the venerable Canon 85/1.8 and for the past four years I've owned the Canon 85/1.2. Of the later, while I've had very good results, I have had some reservations at times. I rarely shoot with the lens wider than f4 or f3.5, it has fairly strong chromatic aberrations wide open, and it could be slow focusing in low light.
With the Sigma, I routinely shot at 2.8 with exceptionally sharp results. (I used both my 1Dx and my 5Ds.) I found no issues with focus speed, focus lock or tracking in servo. Though I had been hopeful about the lens, I was a little wary mainly because, though my Sigma Art 50 is sharp, I have issues with the lens being about a 1/2 stop darker at any given aperture compared to my Canon lenses. (I have sent it in only to have them say there's nothing wrong and it's within specs.) I had no such issue with the Sigma 85 when switching between that and my Canon 70-200/2.8 or my 135/2.
I hope to sell my 85/1.2 in the near future and buy the Sigma 85. I actually tried buying the copy I had from lensrentals.com, but they wanted list price for it (though previously rented a few times -- not a biggie for me), but the real deal breaker was that it would only have a 90-day warranty versus Sigma's 4-year warranty. That was one sharp lens. I hated to return it, but can only hope any copy I buy is as stellar.