Ultra-light backpack folk seem enamored with everything Cuben. Does the recently introduced "waterproof/breathable" Cuben work? I am primarily interested in knowing if folks have experience with its durability in North Cascades brush and rock (thinking rips/tears), but also interested in durability from a wearing-out standpoint, degree of water resistance, and degree of breathability. Cuben has enormous potential, but what is the reality?