I'm only basing my review on the AYCE special. Yama is definitely one of the dankest buffets in Vegas, including Wynn and Wicked Spoon. Coming from LA, I consider myself somewhat of a sushi elitist. Although the quality of the fish here is mediocre, the prices here are unbeatable in Vegas. The AYCE also includes all hot foods including teriyakis and tempuras. The only drawback here is that the service is extremeley slow on busy days (which pretty much means every day). Be sure to try their uni, albacore, and sweet shrimp (although the uni and sweet shrimp are only included ONCE in the AYCE). With the benefits and drawbacks, I would rate this place a solid 3 star.
PROTIP: Be sure to try the seafood salad; a mixture of sashimi slices in ponzu sauce and sliced radish.