Is it very common that lenses have defects, like sharpness issues and other stuff you read on internet forums and reviews. The reason I worry about it, is because I thinking about buy some lenses in the states when I am there on vacation. Especially now when dollar is very low compared to the swedish currency. I get that impression when some guys "state" on the forums they have exchanged some lens model 3 times before a good copy turned up. Which makes me believe they write this to show their unsatisfied feeling with some products. Should just lay low and let the money pile up and buy at local dealer so I can be sure that I dont bump into any problems.