Perfect wide angle for crop DSLRs

I bought this lens for my 20D when I found I needed a wider lens than my 28-75 Tamron. All my lenses we constant 2.8 or faster. So when I tried some of the 10-22 variety lenses...I found the viewfinder image very dark and small. AF performance was poor as well. Then I tried this lens and the Canon 17-40 f4. Loved the build quality and optical output of the Canon...but I had constant focus issues with it. I tried 5 different copies of the Canon before giving in and picking up the Tamron 17-35. It worked perfectly since day one. It's a very light lens. Wide angle is very sharp and usable on a crop camera like the 20D or 350XT. Focus is fast. Faster than the canon 17-40 f4.