I'm planning on selling my current XTi and EF-S 18-55mm IS to fund a 40D body. A lens for the 40D that has caught my attention is the Sigma 18-250mm DC OS HSM, it appears to be a relatively new lens, and I can't find any reviews on it. Any opinions on this lens? I have only ever had Canon lens. If I can spare the $ I may end up with a 50mm f/1.8 II and 430EX II as well. Sigma 18-250mm DC OS HSM vs. Canon 18-200mm IS? Comments on the lens?