I found a nice copy of the Canon 28/2.8 last year on the ‘bay, from a seller in Japan. It’s a beautiful lens, very compact and of excellent construction. I haven’t used is on my 35mm film cameras as much as I thought I would when I bought it, but am keeping it nevertheless. Most recently, I’ve used it, with an adapter, on my Leica CL digital, where it stands in for a 35mm equivalent focal length (when I want to use a manual focus lens instead of the 23mm Summicron-TL). On the CL, it’s sharp with moderate contrast. Interestingly, Matt Osborne (aka Mr. Leica.com) did a comparision of 28mm lenses for Leica cameras last year, and the Canon 28/28 scored very highly in his test (I think the top scoring 28 was the more recent version of the Voigtlander Ultron 28/2.0, but the Canon wasn’t far behind).
I should add: I also have the Skopar 28/3.5, which is a super, and super small, 28mm lens. I routinely take that lens with me on hikes in the mountains, in combination with a 50. It produces outstanding images on black and white film, with good contrast and sharpness. There are examples of photos with this lens over on my Flickr. F.3.5 is a bit of a limitation, which is one reason I bought the Canon, but if you don’t need a wider aperture than f3.5 and can find a good copy that doesn’t break the bank, I would recommend it highly.