Well I am here at Sigma to have them once over the lens to make sure it it focusing properly. The tech laughed when I told him about the price gouging on the Canon lenses....lol
I'm actually going tomorrow. 60% of my shots are dead on, the other 40% are repeatedly very slightly back focused. In those situations, if I take a second shot and apply a very small nudge on the focus ring, the results are sharp even when pixel peeping. It seems to be related to lighting, subject size, contrast, and who knows what else. Its obviously an auto focus issue rather than a misaligned element since it doesn't happen all the time. I described it to a tech and he seems very sure it was a fixable issue. I hope so. Any advice when I get there?