It's Starbucks ... so really a review isn't necessary ... it's average coffee, nothing special. I only go to Starbucks because I like their Skinny Cinnamon Dulce latte and because I typically have gift cards from clients and loan officers.
The line here is incredibly long ... and I can tell you know that there is another coffee shop just inside where the doors are to the taxi line at Mandalay Bay and it has a fraction of the line (and probably a fraction of the price, too).