I bought this lens used four days ago. Excellent lens, good bokeh, good focus. One thing I found a little helpful while shooting with a 20d is to adjust your metering/focus settings on the view finder - this will keep you from having to 'focus hunt'. The lens doesn't focus as fast as some of my other lenses but then again, that's good when you're in close.
Since I bought the lens used, I also had a problem with the dust showing up on pictures. Apperantly I need eye glasses because the camera was focusing in on dust I couldn't see until I practically put the lense to my face and searched for it in the light (is that the eye/age thing going on or what?).
Keep things clean and you'll love it! I would highly recommend to anyone that is getting started in macro photos.