AA23 has good potential, although you should always consider whether your hand is suited or double-suited as well... the reason for that being that with hands like A2 and A3 you can find yourself with the nut low, but no chance for the high, and the main profit comes from scooping the pot.
If you have a suited Ace, then you have a better shot at making the best high hand as well (even if on the flop it's only a draw or even a back-door draw), which adds value to the hand.
AA23 is great because of the potential, but if the flop doesn't fit, then it should still be thrown away. If you hit an Ace, you'll have trips (in Omaha mainly considered a drawing hand for a full house, although it can sometimes hold up), and if you hit 2 low cards you'll generally have the nut low draw, and with 3 low cards you'll generally have the nut low made. Additionally with A23 in your hand you're less likely to have your nut low 'counterfeited', and have a better chance of making the Wheel (A2345).
Pre-flop hand selection is important, because hands like that are noticeably better than random junk. However, they're not as stand-out as AA is in Holdem. In Limit you'll still be looking at the flop for a fit. A low will hit by the river a significant proportion of the time, but the big leak for a lot of Omaha players is chasing too much, especially when the result wouldn't be the nuts. In Holdem most of the time nobody has the 'nut' hand. In Limit Omaha H/L (full-ring), you expect to see a nut hand a lot more often.