After all of the great feedback from all of you I ultimately decided on a Nikon D3s. As such, I am looking for a good versatile lens to match it. I have been going back and forth between the Nikon 24-70 and the Sigma 24-70 (new HSM model). I am not pro but this is becoming a pretty serious passion for me, that is why I am making the investment in the D3s. The Nikon is about $1,000 more then the Sigma, but I have read many reviews on the Sigma and most are very positive. Will I be disappointed in time with the Sigma even though I will keep some money in the wallet? Or take the jump and go for the Nikon? Anyone shooting with the Sigma... I have searched and have not found any good comparisons between the Sigma and Nikon. Thanks for the feedback. Jim.