I just got back from a trip to Maui, and want to thank all the chowhounds whose earlier recommendations made the meals such a success. The best meal for me by light years was Mama's Fish House at the start of the Hana Highway. Be forewarned, it's seriously expensive, even at lunch, but the atmosphere and the food were amazing.
I didn't have a good experience at the Waterfront, another board recommendation. I thought the food was straight out of the bad part of the 1970's, and I found the server to be astonishingly intrusive.
On a better note, two sister restaurants in Lahaina, Pacific O and I'o were really terrific - a beautiful outdoor terrace right on the water and light, excellent food. I also really liked Buzz's Wharf in Ma'alea - a more casual place, though not cheap either. Their fried oysters were the best I've ever had - good even if you think you don't like fried oysters. I also had a really good casual mean at Charley's Restaurant, also near the start of the Hana Highway.
Thanks again, or, better, mahalo.