I have yet to play Omaha in any form live. The thing that seems most obvious to me is that it might be somewhat more difficult remembering your hole cards without having to look at them a second or third time. I have a system down to remember my hole cards in hold em, but there's only two of them. That's one thing I really like about Omaha on line is that the cards are there face up, and many times you can catch that unintended straight and it hits my eye where otherwise I might not have noticed it quick enough to benefit.
I've been mixing up my games quite a bit, playing more PL Omaha 8 cash games, which are pretty easy pickins. Last night for example, I played PLO8 .25/.50 and won $40 in an hour, while taking a 4th place (no money of course) in a $33 NLHE SNG and a second place in an $11 PL Omaha game.
People gave me some guff about mixing up games to lower variance, but I'm making more money this way, so why fight it. It keeps me from overplaying NLHE SNGs, as I used to multi-table them. I feel it has a huge benefit mentally, since I'm always thinking. Poker is a thinking man's game and if you can keep the mind alert, I think you make better decisions.