I heard so many good things about this place that I just had to come and try it out last weekend.
The buffet is upstairs from the main valet entrance of the Cosmopolitan, down a long hallway. The venue is beautiful and absolutely love the layout.
The lines get. LONG. I'm talking 1 hour+ LONG. Varied sections from breakfast, Mexican, Asian, Omelette Bars, Sushi and dessert make for a great experience. I love the small pans & cups that portion the food for you.
Overall, I would come on a weekday or early on the weekends to get through the madness of after-clubbing, crazed kids.
Also, check in on foursquare to get speed check-in!