Right now I can confidently work from three feet to my subject with the 85mm, but, if I'm understanding the focus shift problem, the "real" working distance with the 50mm when using AF is about four feet. While there might be times I used Live View for static subjects, I'd mostly be using this for creative portraits of paying customers and soon-to-be-delivered first child.
Another little twist somebody added to this thread was a mention of the 50mm 1.2 being improved in and after 2010...Does that mean the link referred to in Sporgon's post is now out of date???
My understanding is that the close focusing issue was improved, and my 2 copies haven't exhibited horrible issues that I've heard about. Here's a shot at minimum focus distance (at f/16, so not a great example) but the focus was fine. I think I hit the AF button two or three times to get it perfect, which is what you have to do at MFD, but that took all of 3 seconds.
With the 50mm focal length, you generally don't want to take portraits from closer than 3 or 4 feet anyways as it introduces enough perspective distortion to make noses look big and things like that. I typically use the 85 and 50 at roughly the same distances - usually 6-20 feet away depending on my framing.
I've lost shots at times because I was too worried about switching to the appropriate lens during the extreme pollen times we have in our area--especially on windy days.
In a way, this discussion of changing lenses is pertinent, because many of us seem to agree that both the 50mm and the 85mm are lenses for specific shots, not for the majority of work at an event. Having the confidence and competence to swap out quickly when needed is, in my opinion, one of the basic requirements of a topnotch photographer. Otherwise, why use a DSLR? I wish I could get faster and not be so worried about dust.
With the older SLRs like the 5D classic and somewhat with the 5DII, dust was an issue, particularly for landscape and macro shooters who typically shoot at f/11-16 or even f/22, but with the newer bodies, I think people are a little overly paranoid about changing lenses. Unless it's a really windy day, say 20+ mph winds or a really dusty environment like the beach, desert, or dry mud, I wouldn't get too caught up in things. If you point the body down and use yourself to block the wind, you can change lenses without much fear, even if it takes 1 minute or so. I live in a place with TONS of pollen and that's never been an issue. As you say, being able to change lenses IS the whole reason for an SLR, after all