I don't own the 85L because I don't have a use for it (had 85/1.8, hardly used, sold), but I was offered a chance to test drive the 85L by one of my dealers who was trying to make a sale
I took a couple of frames wide open and I was absolutely floooooooooooored by the sharpness on my 5D. It was as sharp at f/1.2 as the 85/1.8 was at f/2.2 or 2.5. A lot of people saying the 1.8 is 'just as sharp' are not shooting wide open - there is nothing wrong if you don't shoot wide open or you don't need that crazy aperture, but if you DO need the aperture, that's the way to go. I wasn't happy with my 85/1.8 at 1.8.
So in that instant I understood why the 85L commands such a huge price premium.
Took the CF card home and peeped it on the monitor. Absolutely amazing. I could see every hair on my subject's head and that's where I learned the words "PLANE of focus" - the DOF is so shallow, there's no depth!!
If I needed that focal length I WOULD plow down the $$ on the 85/1.2L without reservation, it's just that I don't need that FL and aperture. If I was shooting f/4 or below, I have two lenses covering that.