I've used quite a few 50's, including the Canon ones (excluding the f/2.5 macro), the "Sigmalux", Oly OM 3.5 macro, Zeiss f/2 ZM, Rokkor, and every single one of them has been very different both in output and in use. The Sigma is really very great when it hits, but AF is so utterly unreliable that you can never rely on it at large apertures, even after proper calibration. That is a shame because the optics are very good. Even so, I still prefer the 50L even if it is not necessarily sharper than the Sigma at 1.4. Not everything can be easily quantified. The Zeiss was excellent, but I simply did not like the way it rendered. It was too "clinical". I find the 50L is amazing in every way: bokeh, color, contrast, build, weather sealing, reliable af, and most importantly, I really love its overall dreamy yet punchy signature. If you measure the value of lenses in sharpness only, then no, it is not worth it's asking price. However it's plenty sharp for my use, even wide open (in the centre).