Late last fall I purchased the Canon EF 35mm f/2 IS USM lens here in Switzerland.
I had waited some time after the introduction for the initial price of the lens to drop to a more reasonable amount. My reason for purchasing this lens over for example the Sigma 1.4, was it's more compact size, the relatively fast aperture and the image stabilization. I also intend to use this lens on 70D camera in a water housing and try some underwater portraits. I have jet to get around to that...
On the other hand I have had a number of opportunities to use this lens on the Canon 5Dmk2 as well as on the Canon 7D. On the 7D off course the lens morphs into more of a standard 56mm lens and performs admirably. Very little light fall off and it's tack sharp.
The lens is no slouch on the full frame sensor camera either, producing sharp images and the bokeh is quite nice too. Here the lens does show some light falloff wide open, but disappears at around f/4. The AF speed is very quick, precise and nearly silent. I very much like the look of the images this lens renders, there is a certain dept to them.
Canon 7D, 35mm f/2.0is ISO-400 1/200sec. at f/6.3
Canon 5Dmk2, 35mm F/2.0is at ISO-125 1/125sec. f/8.0
Canon 5Dmk2, 35mm F/2.0is ISO-800 1/20sec. @ f/8.0
Canon 5Dmk2, 35mm F/2.0is ISO-200 1/200sec. @ f/3.5