I've been using the 17-40L both on FF and crop - will probably upgrade to the 16-35 F4 at some point - a great focal length for both formats.
I had the 17-40 F4 L for over 8 years and loved it despite it's quirks. The Canon 16-35 F4 L IS keeps the wonderful colour rendition of the 17-40 but adds sharpness and loses distortion - it is just so much better in all respects, except the damage to your wallet!
Just buy one - you will love it!





