[Atropos]

Yeah I think greywolf got it right. I remember reading in Ciaffones "Omaha Holdem - The Action Game" that pot-limit is the best structure for Omaha, because the opponents can be observed over multiple betting rounds, in nolimit nearly every hand would be an all-in fest from the flop on.
I personally believe, that the variance in pot-limit Omaha is already very huge, but making the game nolimit would make it a real variance hell. I mean the starting hands are so close in value, playing against a LAG preflop would be very tough, then going all-in on 53% shots on the flop wont help much too reduce variance.