I use it when I want a fast moderate wide lens on a 1-D2 body (crop factor or 1.3x, or about equivalent to a 35mm lens.) If I'm using this lens, I'm shooting at f/2 or wide open; otherwise I just use my f/2.8 zooms.
It is reasonably sharp at f/2, quick to focus, etc. It makes a nice combo with the 85/1.8 on a second body for low-light documentary photography.
Is it the world's greatest 28mm lens? No. But it works pretty well when I need the speed.
I have not used it very often on a 1.6x-crop body, so I can't comment on how it works as a "normal" lens, but it ought to be fine.