I bought the 17-55mm IS f2.8 based largely on careful consideration of reviews on this site. One thing mentioned on other forums, but not this one, is the dust problem inherent with this lens, that is: it has a propensity to collect dust internally. Never-the-less I purchased this lens and sure enough itarrived withhalf a dozen large specks of dust inside. Is it possible to comment on this within your review? There must be a serious design fault if the lens atracts dust like this.