I have been playing PL 200 and PL 400 and I have been limping with a variety of hands (QQxx JJxx 910JQ, and from early position even KKxx and AAxx). The reason that I do this is that I find even very strong hands hard to play out of position, and for the most part (unlike in NL holdem) i can get away with limping preflop to see a cheap flop. The advantage of this is that I keep the pot small and can fold to a bad flop/lot of action on the flop, and my experience is that raising doesn't really weed out the bad hands as people will call with a huge range hoping to hit the flop. I'd be interested in the thoughts of any experience omaha players on this strategy. My understanding is that the received wisdom is that limping preflop is bad/weak play, but my experience doesn't bear this out and I'm curious of what others think.

I don't think that's the received wisdom at all. Position plays an even bigger role in Omaha than in Holdem in part because the danger of giving free cards forces people in early position to bet their hands. Thus, you should actually be more cautious preflop when you're OOP. You should be raising premium hands from any position, but limping the more marginal or speculative hands in early position when you think you can see the flop cheaply is perfectly appropriate. In fact, your starting hand selection may even be a bit loose in early position. The value of a hand like JJxx in early position depends entirely on the value of the xx. But I play quite a bit tighter than the others on this forum.

Weak tight is quite profitable actually.

I usually limp from early positions as well. Not QJT9 tho. That's definitely a raise from early positions and a 3-bet from CO and Button