Kane Edition has special skins for certain units and comes with an extra DVD with some bonus content on it, purely for watching. For example, developer strategies and cutscene bloopers. The special kane steelbook edition which you can get from The software boutique(dont know if they still have stock) comes with a Nod/Gdi  t-shirt, a dog-tag, a poster, a razer mantis mouse pad and a tiberium bag(last one is gimmicky)