My original Tan Smart Cover has had some major adhesive failures where all around the edges and hinge then the layers have separated. AppleCare considers this normal wear and tear and on several occassions refused to replace it so I've decided to buy a new smart cover but am wondering if Polyurethane held up any better over time. So does anyone have any opinions regarding Polyurethane vs Leather durability? Does poly fringe less around the edges? How is yours (leather or Poly) holding up?