Most anti-third part lens comments I've seen come from Ken Rockwell, but I don't really trust him. My curiosity sparked when I was visiting one of my friends, who is also an experienced and talented photographer who had just picked up some good L glass he was showing me. After I told him I had a pretty good lens coming, he wanted to know the detail. I told him it was a Sigma, and he winced. "I dunno man, third party lenses...". I've also seen some people around this forum who dislike third party lenses. Most tests show that even though most are not as good as their Nikon/Canon counterparts, they are pretty damn close and a lot cheaper. Is there another detail I'm missing?