Though I'd hardly consider Orange County the equal, culinarily-speaking, of LA proper, or SF, it had its moments (for me), having worked there for a few years. Sushi-wise, I had some very fine meals at Sushi Shibucho in Costa Mesa, easily on a par with those I had in LA or SF. Though I never had the opportunity to try them myself, places like Abe in Newport Beach, or Wasabi in Tustin, have gotten consistently good reviews as well.