Has anyone had any experience with Sigma's HSM lens compared to Nikon. Also How are there Teleconverters. I saw on their web page that they are coming out with a 300 f2.8 hsm in April. From what I've heard from them it should be about what I was wanting to spend. I've never had much luck with sigma, but I've never seen one of their better lens. Any advice or experience is much appreciated. Drew
