I just got back from a week on the Big island. Although food was not the focus, I did manage to try a few places I had read about.
Ate dinner at Pahuia at the Four Seasons and I was a little disappointed after reading the rave reviews posted here. Great dining spot especially at sunset, attentive friendly service, beautiful decor, and they gave me a table in the front row even though I didn't have a reservation. The food was fresh with interesting ingredients, unique presentations, and great preparation. But ultimately, I didn't totally connect with the chef and his style of cooking.
The same goes for O's Bistro in Kona. My main course just didn't work although everything else about the place was very good.
Quinn's in Kona had good fish and chips. Good spot if you are looking for a nice beer and some basic food with a local flavor.
The Coffee Shack near Captain Cook was perfect for a re-fueling stop during a road trip. I had a good breakfast at Ken's Pancake in Hilo. I couldn't make up my mind which pancake to order (Macadamia nut, banana, or coconut), so they put all three on my plate. Perfect for a long hike out to the lava flows.