I was there for the lunch buffet . . . . the restaurant was not even half full. I assume that there were not many patrons since most people just stay at their hotels / casinos for buffet. This actually made the experience much better. There were no lines, and the food was still very fresh. There were a great selection of sushi, and various other Asian dishes.
Hint: Go to the Tix 4 Tonight kiosk in front of Planet Hollywood for a discount coupon (cost 2 dollars), and you get about 5 dollars off the lunch buffet price.