The Wynn brunch buffet is one of the best in Vegas. Between this and the Bellagio buffet, you can really get your money's worth. I have only been here for the brunch, but it is always excellent.
My only complaints are that the crepes they service are seasonal ( I've been here 4 times and only had the crepes once). Do not even bother with the candy apple either, unless you A. want to have an emergency dentist visit or B. do not care about your 2 front teeth. That outer coating is hard as a rock.
The best parts of the buffet are the mini waffles and the thick cut bacon, which is almost like a ham. Salads and dim sum are also excellent. My friends loved the eggs benedict, but I am not really a fan of them in general so I am not sure.