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The few people who have already gotten the new lens all seem to be raving about it and the tests that LensRentals have done on their five copies show very little copy variation and image quality that is better than even the best current lenses Canon has.
This doesn't mean that what you're seeing isn't true, but it might be an anomaly. How have you gone about testing your new lens to determine whether it's sharp or not? Did you auto or manual focus and if AF, did you do the AF MicroAdjust for your lens? Was the camera on the tripod or handheld?
If there truly is a problem with the lens, I would either return it to where you bought it or send it in to Canon to have it checked out. If there's a problem, they'll find it and fix it, but it sounds to me like you either haven't given it a good chance or you did get a defective lens. It does happen, but it seems to be less often than in the past.