Went to Chandelier twice during my weekend stay in Vegas, but really only remember one time (stone drunk the other time...and that's before I even got there).
The bar is absolutely gorgeous, with two and a half floors of lounge and bar space. I say 2.5, because apparently the first floor and second floor are "not as cool" as floor 1.5 (you need to use the stairs to access this floor).
Lots of talent, great drinks, and a great place to people watch in Vegas.
Especially if you cannot get into Marquee, Chandelier is a great second option, not just inside Cosmo but in all of Vegas!