I've been looking to sell off my old Sigma 70-200 2.8 and get something with more on the telephoto end so that I'm no longer frustrated whenever I really want to zoom in on something. I've seen a lotta good reviews for the lens that has been nicknamed the "Bigma" (the Sigma 50-500 f4-6.3 EX). Has anyone here ever owned or used one? Did you like it? I do have a good tripod for the 500 end. How far can you handhold it? Ever feel limited by the slow glass?