Neuro, Thanks for the info - I did notice a significant difference from the first (16-35) to the second one. But still the second one was not any better than the 17-40 at 4.0 (comparing the 16-35 at 4.0 to the 17-40 at 4.0 - and again both at 4.5). At 2.8 I was not happy with the IQ at all (24mm and 35mm is what I mainly compared). I used AF with the center point focus on the 60D aimed at several high contrast and detail subjects (things that normally would show up in pictures that I would use the lens for). On the second lens I tried flat subjects (like wall calendars with a lot of contrast, detail and color) and 3D objects (flowers, etc.).

To get the (indoor, available-light) photos I was pleased with on the 16-35, I always ended up using a flash...which I could do just as easily with the 17-40 and get the same picture.

Believe me - I really wanted to like this lens!

I don't understand what you mean about sending the camera and lens in for calibration - If you don't mind could you explain that? (or point my to a link where it has probably been explained many times before!!!) I have a 70-200 2.8vii; 24-105; 100 2.8L; 300 f4; 50 1.4 in addition to the 17-40 - and all of these focus accurately and I am very happy with the IQ they provide.

Thanks for the help!
Brian