Basically, anywhere at the Four Seasons is worth your time (and $$). I haven’t been to Spago yet, but friends really rave about it. And I LOVE Duo and Ferraro’s.
Ka’ana Kitchen at the Andaz is a farm to table style restaurant that serves dinner plus a daily lavish breakfast buffet. Most of the kitchen is actually in the middle of the restaurant, hence the name and it makes for a fun atmosphere.