Summary: I not only shoot A mount- I shoot full frame for this lens and this lens- period. I've got numerous systems (M43, APSC, FF) and what I can say is it comes down to glass. In terms of application, I work weddings with this and a 50mm zeiss.
Summary: This is truly a 'unicorn' lens as others have testified. I've used a bunch of dedicated portrait prime lenses, usually in the 85 to 100mm range, but this one is the best so far. Tack sharp, brilliant color, gorgeously round bokeh.
Summary: I got this lense to use with the LAEA-4 adapter on the a7ii. I'm not a pro so only have my personal experience but once I calibrated the focus it was simply amazing. I have read people rave about this lens and in my mind it is truly "legendary".
Summary: I have been using this lens for a couple of months. It is the best lens that I have owned. I use it with my Sony a65. As an amateur I have been learning my craft and this lens has made a huge difference.
Summary: This lens is the pinnacle of technology and optical quality for portrait artists. Though a bit on the heavy side for use on mirrorless A7R but I have not taken this lens off my camera ever since i received it. Images are rendered beautifully and the bokeh at f/1.8 is amazing.