I owned the EF 17-40mm/4 years ago and did not like it, other than the affordable price. The corner sharpness was poor. Plus it lacked image stabilization. I was so happy when I upgraded to the EF 16-35mm/4 IS and got a noticeable boost in sharpness, and I could shoot with longer shutter speeds and lower ISO in indoor/night situations.
Not a budget lens, but it was extremely good value for money at the time and had excellent image quality for an ultra-wide zoom. Later lenses were better...