Half an hour after I got this lens I started thinking of sending it back. I was testing its focus and it was front focusing. I was able to fix this with the microadjustement on the 50D but then ironically it stopped doing this after a short while and had to bring the microadjustement on the camera back to 0.
The purple fringing that shows in the oof part is sometimes annoying. Stopping down the lens to f4 will make the fringing almost totally disappear.
On the positive side, the lens is super sharp even at 1.8 and has nice contrast. The bokeh is not to die for but it is not bad either.
I already have the 70-200 f4 L and I got this one for low light indoor conditions. In terms of shaprness, the 85mm is on par with the L lens at least in the center. But everything else it is not comparable to the L lens (contrast, bokeh, presence of CA, etc).