When I bought the 5d mk1, I sold my 15-85 and bought the 17-40L. This lens does double duty on the 60d and is a really different animal on either camera.
On the full frame 5d camera, the 17-40 is a very wide angle lens. It's listed as a 17-40 lens and at infinity focus this is generally true. However, it has focus breathing and it zooms in as you focus on close objects. The EXIF data reports 19mm rather than 17mm, so it might be a little tighter than you would expect.
The lens is perfectly good on the 13 Megapixel sensor and it's not terribly soft. That all changes when you mount the lens on a crop sensor camera, such as the 60d. The pixel density on the 60d is a lot higher, and the 17-40L just isn't able to give the resolution required for sharp images. At anything below f/8, the corners are muddy.
I would never recommend this lens for a crop sensor body. I use it on my 60d, but only when I can use f/8 or a smaller aperture - such as when I do long exposures at night.
The 17-40 is a lens with a few flaws, and a price to match. It's one of the cheaper L lenses when bought new or used. And on a full frame camera it is really wide and inspiring. For the money it's a very fun lens to get into ultra wide angle but I would recommend the new 16-35 f/4 if you can spend the money.