I haven't used that lens, but I've shot a decent number of portraits with a 50 f/1.4. What I found frustrating was that as much as I wanted to shoot at 1.4, I could only do that with one person because the DoF was so shallow. You can focus on one eye and still have the other eye out of focus if their head is tilted. But a well focused shot at 1.4 can be absolutely stunning. So I would imagine 85mm and 1.4 (or 1.8) would be the similar, but an even thinner DoF.

So what I found myself doing was shooting some shots at 1.4 or 2 as well as some at 2.8 or 4 for "insurance" in case wide open shots didn't turn out.