Ray although i don't have the Sigma, i have the Tokina 12-24mm and this is my most used lens. These wide angle lenses are very versatile lenses, for me i take mainly landscapes/seascapes but Dave's examples show just what can be achieved also check out
www.contaminationzone.com a site belonging to Pixalo member Nursepayne who i believe used the Sigma 10-22mm for most of the shots on her site.