I am local and have the breakfast buffet from time to time. I think it is a good deal for the price (with card). There is always fresh fruit and some seafood and there is always somebody who will make you an omelet to your specifications..
I am comparing this to the buffets of the local Station casinos which are not so good. The South Point buffet seems to be fresher and has more choices.
I have not tried the themed dinner buffets yet, but I went once for the Sunday brunch which was not worth the money.
Some of the guys who serve you the drinks are only there to count their tips and forget to serve you. In my experience the lady servers are better and more attentive.