As Canon caught up Nikon's lead in developing her 18-200mm superzoom only in Dec 2008, I can't help but want to check out both the Canon 18-200mm F/3.5-5.6 IS and Nikon 18-200mm F/3.5-5.6 VR II lens as a consolidator lens. In short, both the Canon and Nikon lens are comparably well built, focus well (though the Canon AF is much more noisier) and relatively sharp throughout the entire zoom range.
Price wise, they are both priced at about $699 today. But being a Nikon user, I can, but use the Nikon's (unless I attempt to use the Canon-Nikon mount converter).