Ever since I sold my MC version (MC 58mm f1.2 that I wrote in April) of this lens, I had regrets. I have been on the look out for a replacement. According to most sources, the newer MD 50mm version is sharper than the MC 58mm version, but in my hasty test, I found the MC to be better, both in terms of bokeh and sharpness. But they were shot on two different cameras (1D Mark II for the 58/1.2). Of course I will need more time to get to know the new lens and use it for a while before I can conclude. One thing is for sure, the MC 58mm f1.2 is heavier and has an eight blade aperture and the new MD 50mm f1.2 has only six. This will affect the bokeh for sure, either good or bad.
In terms of using the lens, I think I prefer the newer MD 50mm f1.2. It's lighter, focuses very smooth and balances well.
Will update how it performs after some use.
Old Car -- G1 & Minolta MD 50mm f1.2 @ f1.2
G1 & Minolta MD 50mm f1.2 @ f1.2