I have owned the Canon 7d and 17-55 2.8 combo twice. Both times the 17-55 2.8 was stellar and did not disappoint. But at more then $1000 for just the lens, I would have been very angry if it was anything less. The Fuji 18-55 lacks the constant aperture of 2.8, but it is less then half the size and close FAR less money. However, as sharp as the Canon 17-55 was, I think that the Fuji is just a little sharper. I loved the Bokeh that the Canon lens gives, not as nice as a FF but pretty good overall. The Fuji lacks the bokeh, out of focus rendering is nice, but not as strong as the Canon. But again, if size matters [and for me, it is the most important aspect] then the Fuji offering is darn nice. Extremely light and compact.