i can get your point, but from a service standpoint i am always hating the poly, it gets pulled apart, and cut too easily.
plus, i am talking mainline moslty. you would not do poly mainline would you? and how would you secure the valves and such so it doesnt leak? on a main...if you used it>?
i know of most of the fittings available for poly, but dont see how they dont leak a little bit, especially if used for a main.