I bought this lens second hand in Paris in August 2006 for about £600 (I paid about £700 and got the Canon EOS 50e 35mm camera body as well). I wanted a very wide angle lens for my full cropped 5D. I purchased the 24-105mm f4 L with the 5D and whilst this is a very good walkabout lens and is quite wide at 24mm, it is not wide enough for some situations. Also at 24mm you can notice quite a lot of distortion. Having purchased the 10-22mm Sigma for my 350D I wanted something that could go that wide. The 17-35 second hand was only marginally cheaper than buying the new 17-40 f4 L lens, but the fact that it was f2.8 all the way through - something I particularly like - swung it for me. I have read some critical reviews of this lens (as I have of all the Canon wideangle L lenses), but I am happy with it and think the distortion less than at 24 on the 24-105 L lens. The range is perfect for wide angle on the 5D.