I am using a canon 1100D at the moment but want to upgrade to a 7D next year. I would rather spend my money on lenses at the moment as I think most would agree this would be the best way to go. I do have a sigma 10-20 3.5 lens which i am getting good results with and also a canon 20-35 EF which I also like very much. I am indeed no expert but do want a lens that is a little more versatile. The 2.8 aperture is attractive and the slightly longer focal length of the 17-55 is also attractive. I would like to compare both lenses side by side to be honest to see any differences so i am thinking of hiring them from a local camera shop if they have them.