Upload & Sell: On
I had the Canon 180 for a couple years, I loved the OOF backround and sharpness starting at about F4.5. It is not super sharp at full aperture, at least mine wasn't What I didn't like most was the slop in the focus ring when using MF, you end up turning the focusing ring back and forth until you get it. I didn't find the focus to be slow, a common complaint, providing you are close to being in focus already. If you are not it is annoying.
I ended up selling it and buying a Sigma 150 2.8 OS which beats the Canon 180 in every way except FL. It is fully usable at 2.8 actually brilliant, peaking out at about F4. The manual focusing is perfect, no slop plus it's stabilized. Photozone highly recommends it but does note that the Bokeh could be better. I would agree but it is also good enough that I have no complaints. It has become my favorite macro in a matter of days. It also takes all of the Canon made converters. Good luck with your decision.