As some pointed out, the EF85 1.2 II does have optics and AF that are not easy to use. Such were my thoughts when I rented a 85 1.2 II and used it on a 5D1. Focus was not easy to achieve always and it was slow. I also borrowed a 85 1.8 from a friend of mine, that was way easier to handle, but did not like the images too much.
Later on, I bought a 85 1.2 II used, because - like Mr. Wilde - I just couldn't resist temptation. f/1.2 is sooooo much more light than f/1.8. DOF-shallowness also. While focus is still on the slow side, I find it not difficult to achieve perfect focus with the excellent AF system of my 5D3. Focus by wire becomes the new standard with STM lenses anyway, and I got used to it. Yes, it still feels strange.
Since, I have just fallen absolutely in love with that lens. It is amazing.
The IS in the new 85 1.4 lens will be a game changer, I believe. Probably that lenses greatest asset. A real advantage over the 1.2. The rest (AF-speed, build quality, image rendering, colour rendering, price) remains to be seen, however.
I doubt I will ever sell my 1.2 II, but if I didn't have one already...