I recently sent my second copy of the Sigma 85mm f1.4 back as I was still dissatisfied with the amount of misfocus it was getting at closer ranges. I was juggling between the Canon 100mm f2.8L Macro lens and this one for a while, until I saw the bokeh this one produced, and for over half the price.
In one word, this lens is: brilliant. It hits the target every time, and is extremely sharp wide open at f1.8. The Bokeh it produces is creamy as butter and the USM (Ultra Sonic Motor) is silent and fast. Even in lower light this thing hits focus very quickly, as opposed to the Sigma f1.4 which was just hunting back and forth in medium to dark lighting.
The lens is fairly light, which when compared to my Sigma 35mm f1.4, is a nice chance to relax your arm.
It’s great for filming too, the focus wheel is loose enough that you don’t shake the camera trying to turn it, but rigid enough that you can do smooth focus pulling.
Though it’s made of plastic it seems fairly sturdy. I wouldn’t want to drop it (nor would I want to drop any lens to be honest) or get it too wet though as it is not weather sealed. I heard someone saying that theirs got sand in the motor when they took it to the beach so I would be weary of exposing it too much to the different elements.
All in all, it was well worth the £280 I got it for!