The best food on the north shore area has got to be the Dolphin. Great fish, grilled meats and an excellent salad. Go early, hang out on the lanai, watch the rain and the geckos drink mai-tais and make friends with the waitstaff. The ahi sashimi is very good too. For cheaper food, also in Hanalei, try Tropical Taco and Hanalei Pizza (i think). Gaylords at Kilohana Plantation is beautiful for lunch and has pretty good food. Dukes and Roy's on the South shore are both quite good. I was not that impressed with Bamboo Bamboo or Postcards.
