On a DSLR with 1.6x like the 20D, this is the perfect general walk-around lens. Almost tack sharp at 2.8, it just becomes much better as you closed down.
The less than 2x focal coverage from 20 to 35mm is too short. I would have preferred up to 50mm, or at least 40mm.
Even though kind of bulky, the lens feels good and well balanced in hands, and is solidly built. Not cheap construction like some other L lenses.