The presence of sets in pot-limit Omaha has no such value, as in other poker games. Feature of pot-limit Omaha is that when five cards are opened, almost always someone has either straight, or flush. You can form a set on the flop, even the top set, and lose big amount of money if you call raises.
Consider the following situation. Player 1 raises pre flop with A♠A♣7♦2♠, second player calls. Flop is A♥Q♣4♥. First player raises and receives re- raise. What would you do in this situation? Some of you fold, some go all-in. Assume you go all-in, second player calls and shows his cards K♥J♥T♦9 ♠. It's very strong hand with this flop. Second player has 17 outs: 9 hearts, 3 kings, 3 jacks and 2 tens. Probability of winning with 17 outs in Omaha in this example is 66, 3%. First player of course also can win if none of 17 outs will come or if he draws to full house. But probability of drawing full house is much lower – only 37, 8%.
As you see sets in Omaha are very dangerous to play.
If top set you should play very carefully, then, of course, youngest set you have to play very, very carefully even on flop without straight and flush draws, except when you play one on one, because top set can beat you. Let's say the flop hits J-7-3 and you have set of threes. One player starts to attack you. What will you do with this hand?
If someone makes a bet in Limit Omaha Hi, and you make raise, in some cases, your opponent folds, and in some - calls. However, assume he makes re-raise. Does this mean that he will beat your combination? Now you should use all you skills in poker. However, whether he'll beat your combination or not, you still have to play...
However, this is limit Omaha.
In pot-limit, if you raise to increase money in pot, your opponent can do enormous re-raise. So what will you do in this situation? You may play this hand on flop but you shouldn't make a raise. If you make a raise, and receive re-raise, probably your set of threes is very bad hand, so be very careful if you have youngest set on flop.