7 out of 10 points and not recommendedgood build, good sharpness from 5.6 & from 24mm (APS-C), good contrast and color.VERY BAD sharpness at 17-22mm in corners and slightly on edge (APS-C), very high price, heavy.
Before I bought this lens I got some samples from the web, great photos. After I bought it I made some myself similar to the ones from the web (eg.: leaves surrounding a window). I couldn't get the image sharpness like on the samples although I set max sharpening on camera, high speed, 200ASA and f8 or f11. But in the web samples EXIF it says that they were edited in Photoshop CS2, so I opened my 350D jpg files in CS2 and sharpened them a bit (smart sharpen) to match the sharpness of the web samples. Maybe the web samples were made as raw files, but this doesn't change the fact that probbably most of the samples from the web do not have natural lens sharpness, they are sharpened by in-camera and computer software.reviewed June 29th, 2006 (purchased for $815)
My main problem with the 17-40 4L was mainly the sharpness in corners at 17-22mm. On the samples from the web it was perfect. Maybe my lens was not good, but I changed it to another one, a bit better, but still not satisfactory. I don't need an expensive Full Frame lens witch is not sharp on an APS-C camera. It must be terribble on a FF camera.
My other problem was that the lens could not set the sharpness correctly on some good contrast objects in slight dark light (eg.: 1/5s, f4).
My greatest surprise was that my KIT lens is sharper at the edges at 18mm than 17-40 4L is at 17-22mm.
I am very disgusted by Canon 17-40 4L USM, and I returned it to the shop.
Maybe I will check-out Tamron 17-50 2.8 (APS-C), maybe it is better for an APS-C camera.