I disagree. Sealskinz ARE waterproof when bought. Eventually with wear they are not, but are still, as Ady says, some use. You can prolong their life by washing them as seldom as possible and never in detergent in the washing machine. I keep mine clean by wearing them with thin liner socks inside and Shortie Event gaiters outside. I don't see why running should wear them out faster than walking, after all walkers often do more miles than runners. I certainly run in mine and feel I get reasonable wear out of them.
As regards the fit, I like the rather loose style as it does make it easier to wear liner socks inside (which also make them warmer). However I understand Sealskinz have now re-vamped them to give a tighter fit.