I've been thinking for a while about selling my 15-85 since I'm not satisfied with the quality (good at 15 sucks at 85) and the colors that are "weird" (tough to describe) and because , anyways I was wondering if the 17-40 would be an upgrade IQ wise. I was also considering the 16-28 tokina for the 2.8 if anyone has experience with that lens.Can you post some sucky images at 85mm? I have the 17-40 and I was thinking to get the 15-85 because it is a more versatile all-around lens. I'm not planning to sell my 17-40 though, because I use it on 3 cameras(2 ff, 1 aps-c). 17-40 is very good if you can live with the lack of IS.
What I love about 17-40? Its build quality, size-weight, color rendition and the lack of flaring! I find its IQ well above average, especially at f8-11.