Aida, here are my restaurant recommendations. We really loved:
Mama's Fish House (I'm a vegetarian, so it wasn't *quite* as exciting for me, but my boyfriend said he would have gone there every day if we could have--it is located in Pai'a, which is near the airport and on the way to Hana, if you end up driving there)
Merriman's (my favorite restaurant of the bunch, it is located on Kapalua Bay beach and had absolutely fantastic service and really great food; the waiters even took photos of us on the beach at sunset)
Plantation House (in Kapalua)
Sansei (in Kapalua)
Banyan Tree (in Kapalua, at the Ritz)
Mala Ocean Tavern (beachfront in Lahaina, a little more casual than the others on this list--not that anything in Maui is very formal!)
Pacific'O (beachfront in Lahaina, really good food; one of the nice things about this restaurant is that it is next door to a sister restaurant, I'O, which had a luau, so we got to watch the luau for free because we sat outside)
Restaurants to skip:
Gerard's. Honestly, I can't say enough negative things about this place. After assuring me that they would make me a fantastic vegetarian meal I got a plate of steamed broccoli and cauliflower. When I expressed my displeasure they didn't do anything, and even though I didn't eat the meal they charged me $30 (for a plate of steamed broccoli and cauliflower!). My appetizer and soup were also disappointing, and my (non-vegetarian) boyfriend didn't like his meal either--it was small, poorly cooked, and overpriced. The service was slow and not helpful. By far the worst meal I had in Maui.
Roy's. This was generally mediocre, which puts it in the "skip" category, just because we had seven really great meals. It's in a strip mall, which also means no ocean view. I did love my dessert there, however.
Finally, we went to the Terrace Lounge at the Ritz for brunch the day we left and it was fantastic. The servers were so nice that they encouraged us to take bagels and other pastries from the buffet back with us for the flight home.
Have a great time!