Second the recommedation for the Hailemaile General Store - the food was wonderful! Definitely worth the detour.
Sensei and Roy's are also very good; we've never managed to get to David Paul's. I guess we'll have to make a point of it next time!
We were not especially impressed with Hula Grill, although our friends who live in Kapalua like it. For a casual lunch place, we did enjoy Buzz's Wharf, at the marina at Maalaea, where the road turns around the base of the mountains, on the way to/from West Maui.