Reserve -
If you want to get out of downtown, see and be seen at this VIP-heavy lounge notable for specialty drinks and beautiful people. You'll be well taken care of by the table service and if you do feel the need to dance, the floor, while not enormous, gets the job done. The elusive chill-out ambience is captured perfectly, making you feel at peace but still full of energy.
If you do go, it's vital to, well, "reserve" a table in advance - you're not getting seated any other way, and the bar can be packed with singles mingling. But once you're in and enjoying a cocktail in Reserve's red-lit splendor, the trouble will have been more than worth it.