I bought my copy used on eBay a few months ago and must say I am very impressed. The lens is still very high class despite her years old. Autofocus is precise and relatively quick. Image stabilization works well. It does not quite reach up in the same class as my 24-105 L lens but is just a step behind. My copy has the common peculiarity of these lenses that front section loose a little. It should apparently be so according to Canon and I have not noticed that it affects neither the image quality or zooming. Do a second-hand for around 2500 - so buy it. You will not be disappointed.
Its domain is all-around / travel lens, and for this it is clearly sensible objective. The optical quality is definitely approved. The autofocus is quiet and fast, and the image stabilization works well. On an APS-C camera lacks the wide angle, but on a full-frame camera (eg 5D) so it is absolutely perfect!
Very happy with it. well-functioning ice kasnke little ltie wind angle. but works well as a round lens, good skjärpa especially in the middle region. a little too lax, however in the design, slide out (zooming) when ahr it hanging on so