Bryan over at the-digital-picture has completed his review of the Sigma 18-200 f/3.5-6.3 DC Macro OS lens. While Sigma has been releasing a lot of segment leaders in terms of image quality and pricing, this superzoom offers nothing the others out there already do. While it's as good as other superzoom lenses and is priced quite well, it's not a stellar lens optically. That being said, we'd probably take this lens over the Canon offering.
“While the Sigma 18-200mm f/3.5-6.3 DC OS HSM C Lens has an excellent range of focal lengths in a small, lightweight package that doesn't hurt the wallet, I have trouble getting excited about the image quality this lens and any of the other superzooms deliver. Everyone has their own values, and with this lens, Sigma is targeting those placing a high value on convenience and budget. The Sigma 18-200 C is one of the best choices among the APS-C superzooms.”