The Sushi by Jin at Orangethorpe and Brookhurst is currently our favorite place for AYCE. Quality is always good. On our last visit they were a little short handed, but normally the servers are all very attentive and on top of things. At the end of the meal they always offer a small portion of matcha ice cream on the house.
The Ramen place next to Chomp has surprisingly good sushi.
The Sushi by Jin is our favorite AYCE.
Akashiro- Peruvian fusion sushi. Really tasty, but outrageously priced.
Akafuji is a much better value for an Omakase dinner, locally.
The best Omakase value in the area, though, is Sushi Wasabi in Tustin.