I have this lens and my copy is not bad. However, I have the 24-70 f2.8 and 24-105 f4 IS L lenses too which are very sharp, so my standards are high.
Recently, I bought the new Zeiss 50mm 1.4. Although the manual focussing is a pain, the image quality blows the Canon 50mm 1.4 away. The Zeiss has a quality all it's own, almost Leica-like. Now my Canon 50mm sits on the shelf.
Although I bought the Canon 50mm 1.4 for low light candids, I rarely actually find myself needing the f1.4 aperture. I would consider selling it for the right price. It's in absolute mint condition with the original box, warranty card etc.
BTW, my Canon bodies are both FF - 1DsMkIII and 5DMkII.