I picked one up a few months ago from Canon reburbished store. The IS works very well and the subject you focus on is very sharp. However I find the bokeh a bit unpleasing compared to the 70-200 f2.8 (non IS) that I normally use. I realize the 100-400 is not f2.8, but even when my 70-200 is stopped down to an equivalent aperture it just looks so much nicer to me. I am also not crazy about the lens zooming out - and yes I knew that was how it worked when I ordered it. I also find in low light or low contrast subjects it has a hard time focusing in situations where my 70-200 would lock in no problem. It's not a terrible lens by any means, just not as stellar as I expected. Is anyone else slightly disappointed with it?