I have had no issues at all with it, straight out the box it was, and still is, a quality lens. I had a Canon 50mm f1.2L at one point and the focus on that was crazy, back focussing like mad. The Sigma, IMO of cause, is even better than that. I have no problem shooting at f1.2 because the 85mm f1.2L is my favourite lens of all time and is sharp as hell even at f1.2.
I got mine from Digital Depot (members here) and so I could try it first, as I say it is fast and accurate on the trigger.