I had read about this place on happycow many years before, and have shopped and gotten grab and go food on 2 two past trips to Maui island. Was just here again in December 2012, and here's my Hawaiian Moons review update.
This store is small and stocks a range of grocery & natural foods, plus it has a hot foods & salad bar. In the very early days, there were more vegetarian/vegan hot food options, but it was so on my last 2 visits. Vegetarians and vegans can still get food from the salad bar (a bit boring), or in the fridge you'll find a pre-made veggie sandwich or two. Other than that, not so much. The store has added more meat stuff to the hot food section it seems.
You'll probably find a vegan cookie amongst the baked goods.
Definitely go before lunch hour if you want something from the hot foods bar; otherwise, the selection will be meager and appear "old".
Price-wise, the grocery items are on the pricier side. But this is Kihei, a tourist mecca.
The location is very convenient. It's just across the street from the ocean in a shopping plaza with ample parking. Next door is a Maui Tacos where you can get a fast veggie burrito (we did a couple times, but both times weren't good).