From Ken Rockwell's Site:
Up through the 1970s Nikon only made very expensive professional lenses. Normal people had to buy discount brands lenses if they wanted something they could afford. Buying an off-brand lens was, and still is, the worst of all worlds: spending a lot on a camera, and then getting a dinky lens. The lens is the only part that affects the picture quality, so you are far better of with a crummy camera and good lenses.
Nikon and Canon are each primarily lens companies, not camera companies. It's sad to see people buy good cameras and put off-brand lenses on them. The main reason I bought my XTi is to use the great Canon 10-22mm lens!
Enough reason for me! ;^)
You guys know I love KR :^D
Blanket statements like these are what frustrates me about ken rockwell, alpha. How can he reasonably say that every name brand lens is better than every off-brand lens? The answer is he can't reasonably say it, but he says it anyway. The world needs a whole lot more pragmatism and a whole lot fewer dogmatic rants. Better than writing a hundred posts like these on his website would be to go out and actually try some of the off-brand lenses so that he can have an opinion based on fact. </dogmatic rant> edit: fixed grammar