Well... looking at the ingredients list on the Proraso pre/dopobarba cream - it reads exactly like a soap... so one might surmise that it works in a similar way to putting on a watery lather (whilst you deal with making the proper lather)
Personally, I find it is worth it (I use proraso pre/post cream) It seems to make for a more comfortable shave - maybe not necessarily closer but certainly more comfortable.
Personally..splash some warm/hot water on your face..makes the whiskers stand up..I have tried some pre shave stuff...meh..cant tell the difference if your soaps/creams are good quality