If there's one expensive lesson I've learned so far in my brief foray into the world of Omaha, it's that 2nd nut hands don't hold up nearly as well in Omaha as they do in hold-em. So, with that in mind, how should I count outs that improve my hand, perhaps to the second nuts, but won't give me the absolute nuts if I hit them? In hold-em, I would generally give them full value unless they could make someone an obviously better hand - i.e. a card that gives me the nut straight but puts 3-to-a-flush on the board.

Would I be leaving too much money on the table if I didn't count them at all - at least until I get a better feel for situations when they'll hold up?

in multiway pots, don't count non nut outs. when it get short handed, especially heads up, you can give them some weight. If there is big action, someone is likely to have a made hand and not always the draw so if someone goes nuts on a Q92 flop 2 hearts, they are much more likely to have QQ and 99. If its heads up and you have JTh, obviously your straight is good but there is a decent chance the flush draw is good too. Most average omaha players out there don't play hands with enough multiway outs so they will often not have a lot of redraws.

Summary - multiway pots, only nut outs
shorthanded, read dependent, non-nut outs more likely to be good.