I've been very happy with my copy of the 100-400mm (that I bought in February, 2007). It's been around the world with me, dropped (hard enough to crack the casing of the 30D to which it was attached, yet survived unscathed) and I love the range. I've never had any major issue with sharpness, even using extenders that do degrade it somewhat.


I guess I have a good copy. I wouldn't give it up for anything.