I think I'll join this one, but item clause really is meh. IMO, it promotes Tyranitar/Hippowdon/Abamosnow(lol) use. Bold for great justice.
With those pokes in play, your opponent automatically loses 1/16 HP every turn, unless they happen to be immune. Only one poke can carry Lefties and only one ontop of that can carry Black Sludge (should you even be using a Poison type...aka Gengar). While it (the weather) does work both ways, chances are that the person with the Weather-changer probably thought about this before hand (if not, lol) and built a team largely immune to its effects.
So, thus, in the end, you are either forced to die a slow death in the Sandstorm/Hail or build your team around it...despite the fact that you have no Sandstreamer/Hailer. This is just my take on it -- lol at me or my opinion if you don't agree.