I know it's not on the OP's list, but for future reference for others, I stayed a night at Grand Sierra in April and had dinner at their buffet on a Thursday night.

Pros:
-Great service, the best I can ever remember at a buffet
-Big fresh shrimps
-Fresh hot and cold foods coming out even at ~9:30 pm
-Decent value; I believe dinner was $17.95/person

Cons:
-No crab legs on weeknights (though I'm unsure if other casino buffets in Reno offer this anyway)
-Desserts were kind of lacking