I would give this buffet a 4.5 rating.  Wynn's buffet is definitely one of the best ones I've been to in Las Vegas.  I went for lunch, but was able to stay past 330 when they started bringing out dinner food (hahaha).  For lunch they served huge jumbo shrimp, ceviche (even the shrimp in the ceviche was big), cali rolls, prime rib, asian food, etc.  For dinner they started bringing out the big daddy king crab legs, and lamb chops.  the lamb was smokin delicious.  In total, my friends stayed there from 1:30pm to around 4pm.  The service was excellent as well.  Highly recommend it if you're ready to stuff your face in some good food.