Shooting at 1.2 is a steep learning curve, for sure, but really worth it for that dreamy, creamy feel. It works wonderfully for wedding portraiture.
It took me a long time to feel confident shooting with the 50L at 1.2. Be aware that it may require modifications to your technique and experimentation! With such thin DOF you can forget focus/recompose, for example. With the 5D3, which I see you also use, you're stuck with a fixed focusing screen that only shows you accurate DOF to about 2.8, so manual focus isn't really an option either. I found the best tactic is to shoot in AI Servo, because the slight movements of your body and your subject between locking focus and actually taking the shot can make the difference between an eye and an eyelash being in focus! I tend to compose my shot, focus, then fire off a burst of about 5 images, deliberately swaying ever so slightly back and forwards a tiny amount after the first couple of frames. I've found this sometimes adds a keeper or two if the AF failed to nail it!
Have you considered the 50L, by the way? I find 50mm a much more usable focal length throughout a wedding day. 85 is just a bit too long, I find. I'd still love to have an 85L in my bag for posed portraits, but I know my 50L would still spend more time on my camera at weddings - just a thought! Don't listen to the haters, the 50L might not be the best on paper but it still produces bokeh that other lenses can only dream of
Ultimately, anyone who claims high keeper rates with any lens at 1.2 is probably lying, unless their subject is still life and they're using a tripod and 10x live view
Fortunately, the wonders of modern technology allow us to rattle off loads of shots to make sure one nails it!