well just tried it out... its hard to say really what the results were, as i tried a very different blade from my normal choice, and my technique has gotten a lot better these days, so my shaves are rarely very ittitating.
however, i will say this, using a gillette bleue, with the proraso as a pre-shave, i did get a very smooth, irritation free, 3 pass shave. The subtle tingle underneath my standard shave cream was very nice, and my face feels good.
so its probably worth it, given how little you need to use and how long the tub will last. I think certainly it may make the shave slicker, if not doing anything to soften the beard hair. What is unclear, is if you're supposed to rinse after you use it. The instructions suggest just leaving it till it soaks in and then getting on with your shave. Which is what i did.
seemed to work!