I was gonna get a canon 70-200mm f2.8 L IS but my cash won't permit, plus its a lot to spend if it did. I then looked at the 70-200mm f2.8 L (non stabalised) and almost bought one but i have been looking at the sigma version. It would be lovely to have a big white beast on the front of my camera but is it worth it? Is the sigma a pretty good lens? How big is the difference, how much better with a picture be from the L?