One of the things that clearly differentiates No Limit Hold'em players coming to Pot Limit Omaha is how they play the nut flush draw, especially if they are coming from No Limit Hold'em tournament-style.
Basically, if you find yourself all-in playing the nut flush draw in No Limit, you are never in much jeopardy. In fact many players will move all-in themselves, trying to win the pot then and there. The reason that you are nearly always in reasonably fine shape playing this way is that in Hold'em it is comparatively rare for your opponent to have the nuts, such as a hidden set. More than likely you are facing just one pair, and you are near enough to even money not to care, and maybe a small favourite if you have two overcards to the flop. So in the majority of situations, it's hard to make a sizeable error in playing the nut flush draw in big bet Hold'em In many cases the cards are playing you, not you playing the cards, and you are not having to make any brain-aching decisions.
The situation is very different in Pot Limit Omaha.
Because the average hand in Omaha is much stronger, if you over commit to the nut flush draw you are very likely to find yourself against a made hand. This is especially a problem heads up, as you may find yourself getting basically even money on a hand which may be as bad as a 2 to 1 dog, in the case of a hidden set. Time and time again, especially on the Net where NL players are having "a shot" at a PLO game, I see them heave in 100 or so blinds heads up in an un raised pot. Basically they are turning a marginal situation into one that has a very poor long term expected value.
As an example, in a PLO game online a tight player bet into a field of 3-4 players with two of a suit, but no other draw available on the flop. We both have comparatively monster stacks. I passed the nut flush draw! The reasoning was that if I raised, he would either pass, and I would have won a small pot, or he would have re raised, in which case I would be finding myself committed to a bigger pot in which I was a reasonable underdog. If I just called and hit I would not get paid anyway. This is a rare situation but perfectly sensible if you know your foe.
Conversely, in a multi-way pot, if my raise will set me all-in on the flop I am often happy to play the aggressor even though I may expect to get called and I would also expect to have some of my outs in other people's hands. This is because I am still drawing to the nuts, but I will be getting much better money odds and this may actually turn it into a long term positive expectation situation, especially if I have even as little as a back door out extra.
Next time you find yourself with the nut flush draw and little else, think about factors such as position, how big the pot is, whether your raise can actually makes someone pass, how deep your and your opponents stacks are, and how you will play the turn. You can actually decide how to play the cards; they don't have to play you!