Some great shots in this thread. As long as you get a recent, good copy, the 50mm f/1.2 really is the best 50mm option for Canon.
My first copy exhibited some pretty significant focus shift, and so went back to where I purchased it. I then tried several Sigma 50mm f/1.4 lenses, and really liked their bokeh/color rendition, but found the Sigma QC to be abysmal. Each one I tried required anywhere from +15 to +20 micro adjustment to even get close to having accurate autofocus. I thought about going the route of sending to Sigma for calibration, but didn't want to take a chance with them coming back and saying it's in spec (a shame, given the outstanding shots in the Sigma thread). So, I returned the Sigma to the retailer today, and am hanging on to the 50 f/1.2 I also bought last week, as it nails focus perfectly, even at MFD at f/1.2. It's more expensive than the Sigma, but the autofocus is faster and more confident, and I haven't really encountered much of the dreaded focus-shift issue either (it's a UX date code - maybe that helps).