Damage rules. You get hardness, sure, but you're still fully damaged by energy and weapons and suchlike. Plus, it's much harder to buff yourself, aside from the couple of hardness boosts. (Actually it's easier, forget that part) It's still pretty nice, but it's hardly nigh-immortality since destroying the object either kills you or expels you into combat, naked. I thought the whole point was to be an object, and thus incredibly hard to damage and outright immune to almost every attempt to kill you possible since virtually all effects work on "creatures".