www.lenstip.com seems to have some interesting reviews and graphs. They seem a good visual representation of what has been said in this thread by all of you, so I thought I'd post them here.

Left: Canon 50mm 1.2L.......................................................................................................... Right: Canon 50mm 1.4


They do show how the 1.2L is significantly sharper, especially at the center. Interestingly enough, sharpness at 1.2 and 1.4 is not super (in general terms. I suppose it is to be 1.2 and 1.4?), even though quite better than the 1.4.

Also, sharpest f/#s are 4.0/5.6 for the 1.2L and 5.6 for the 1.4.

1.2L graph was obtained on a 50D body. 1.4 graph was obtained on a 20D body. I am not sure how that is affecting the results, if it is.