Summary: I am a prime lens lover for the lower apertures, and this was a great addition to my Canon EF 50mm f/1.8. It's a relatively small lens and weighs next to nothing compared even to some standard zooms. Tack sharp all over once brought down one stop.
Summary: I bought this lens for it's low light capabilities and I was not disappointed. I used it for inside shooting w/out a flash and "freezing" action in good light like hummingbirds. Very "fast" lens. I eventually sold this for it's slightly sturdier and a little faster cousin the Canon 50mm 1.4.
Summary: I have been happy with this lens so far, using it on a Canon 30D body. The glass is decent quality, without any significant vignetting. It's not particularly wide angle, due in part to the 1.3 magnification factor on the 30D, so not great for getting the full room at a party for instance, but works...
Summary: I purchased a MK I version of this lens, have not seen the MK II but apparently it does not have the metal mount that this one does. I like the wide angle, which on a crop sensor like my Canon XTi effectively makes it a 45mm.
Pros: Sharpness, weight, size, value
Cons: Hunts a bit in AF, A bit noisy, plastic and obviously feels less substantial than a heavier metal lens. Decide for yourself what significance these characteristics mean to you.
Summary: Great price for this 2.8 lens if you do a lot of architectural work. On a crop factor body (I used it on a 30D and 40D), it produces virtually no distortion. Only gripes are that is focuses slow and noisy.
Summary: On my 400d this is like walking around with a 45mm lens on a 35, The noise does not bother me at all and the results have been better than I hoped for. It's light ,unobtrusive and I have not used my zoom much since I got the 28. I'm happy with the whole deal.
Summary: If you could only carry one lens for your Canon digital SLR, or you wanted to keep your gear to a minimum, this would be the only lens to carry. Of course, you would be limited in your range of photography, i.e. no large groups of people in small spaces; no sports photos.
Summary: Prior to purchasing this lens I was using the Canon 20mm 2.8 USM and was generally unpleased with the resulys. The lens was very soft wide open and I felt I should have gotten more out of a lens of that price.
Pros: Decently fast at 2.8, Sharp, Nice wide angle on 35mm, Nice close to normal prime on a 1.6 crop body., Built well