The 50L has been a trooper for me. Focus has always been accurate on my 5DII bodies, though it front focused a bit on my original 5D. Bokeh, color, and saturation are legendary with this lens. Sharpness is adequate relative to other L primes, but better than all other 50mm lenses, period.
It's WORLDS better than the Sigma 85/1.4 I have with regards to focusing. That thing is downright schizo in comparison (yet I still have it). I wouldn't touch the Sigma 50 with a 10 foot pole. I don't care how many people claim it's wonderful.
I use nothing but the center AF point with the 50L and have great results. Focus and recompose in general is an art, and getting it just right takes practice of course.
