The 35L is a truly excellent wide-angle lens ($1100). On a 1.6x crop camera (20D, etc.), it has great colors and perspective. On a full-frame camera (5D, 1Ds), it also has the same field of view as a 22mm (35mm/1.6) lens on a 1.6x crop camera, and I find I don't usually need any wider. In fact, the lack of great wide-angle lenses below 35mm had been a big reason for going to a 5D and 35L. On the 5D I'm particularly impressed with the sharpness of this lens. This is due to the lower pixel density, which spreads the pixels out over more of the glass, thus placing less demand on the center of the lens. Sharpness peaks around f/2.8 and can be exceedingly good, but f/1.4 is surprisingly close in sharpness and contrast. The bokeh at f/1.4 is pretty yet limited due to wide angle. I'm starting to groove more on f/1.4 because of the subject isolation and sharpness. Vignetting is quite noticeable below f/2 on the 5D, but it doesn't bother me as I take mostly people shots.

It's plain to see from the pictures below that the best aspect of this lens - aside from not needing a flash anymore(!) - is the up-close personal perspective it delivers on both the 20D and the 5D. It's the ultimate environmental portrait lens, particularly with children. Carrying around the prime forces me to move up close. If I had a zoom, I'd end up in the 50-100mm range out of laziness. Note that the minimum focusing distance is a nice 1.0 ft. On a full-frame, the lens often feels as if it's getting a little too close, particularly with adults, so one other lens to consider would be the 50mm f/1.2L ($1350) but it has a well-decumented back-focusing problem when using the center AF point at short distances. Also, I don't find 50mm a very interesting focal length for 1.6x or full-frame bodies.

For a general-purpose zoom on a full-frame body, I'd get the 24-70 f/2.8L ($1150) because it has excellent image quality, but the 24-105 f/4L IS ($1050) would be more versatile with its extra 35mm and IS. If you need a little wider, the new 16-35 f/2.8L II zoom ($1500) is excellent at 16mm and 24mm, but doesn't come close to the 35L at 35mm. The 24-70 f/2.8L comes closer to the 35L at 35mm, but I'm just starting to really use the 35L at f/1.4 and am too hooked at this point. The 17-40 f/4L is a great value ($680) and works particularly well on a full-frame, but is no match for the 16-35 f/2.8L II. The 24 f/1.4L ($1100) is not as sharp as the new 16-35 f/2.8L II, but it provides f/1.4 for the very few who need it (not I) Canon announced a 14mm f/2.8L II ($2000 ) in August that produces fantastic results for those who need as wide as possible for architectural interiors, etc. If I went ultra-wide, I think I'd go for the 14LII. to really get that different look. In summary, Canon deserves a lot of credit for improving its wide-angle offerings since 2006. To get any better, you need to move into super-expensive Zeiss and Leica glass.

I recommend the The-Digital-Picture.com for comprehensive reviews.