I tend not to harshly evaluate lenses, as I know that no lens will ever be perfect. However, this lens has been a very large disappointment for me (in addition to a waste of time and money). I heard plenty of talk about focus issues with this lens and how it's not much sharper than the EF 50mm f/1.4 USM lens. Still, I purchased it because I expected very good contrast and wide aperture effects (thin dof, pleasant bokeh).
I did experience the above characteristics, but the EF 50mm f/1.2L USM lens suffers from a design flaw: focus drift and backfocusing. The lack of a floating aspherical element means there will be depth of field aberrations when stopping the lens. That is, the depth of field will appear to shift back when narrowing the aperture.
I have evaluated four copies of the lens on two camera bodies (one old calibrated body and a relatively new body), and each copy exhibits backfocusing. Even after compensating for the backfocusing, the lens sharpness at the center of the image circle within the depth of field isn't too good. I compared it against the 50mm f/1.4 USM lens at f/1.4 and f/8. While the 50mm f/1.2L is the clear winner at f/8 in terms of contrast and sharpness, at f/1.4, the 50mm f/1.4 lens actually wins out in sharpness. I couldn't believe it so I exchanged the lens once in May. Same deal. When I decided to give the lens another chance in October, I was disappointed yet again.
People with a need for speed will buy the 50mm f/1.2L USM because of its strengths and in part due to a need for speed. But with severe issues in terms of the focusing and focus drift, I don't think any price, no matter how reasonable, can justify this lens' flaws. If you're looking for a great f/1.2 lens, the EF 85mm f/1.2L II USM will do everything you ask of it. But as for the EF 50mm f/1.2L USM, buyer beware.