Because the sensor on the 7D is smaller than a 35mm film frame, the angle of view is less. Your images on the 7D will be equivalent to those created on a film camera with a 36-157 lens - the lens's actual focal length multiplied by 1.5.
This doesn't really lose anything in sharpness or light-gathering capability, except for the limitations of the 6MP sensor of course. If the aperture is f3.5 on a film camera, it will still be f3.5 on the 7D. The only hitch is that it's harder to get very wide angle lenses, and that's why they're introducing new 17mm lenses. That focal length would be considered borderline "fisheye", on a film camera.