I've been to XS twice and loved it both times. The first time, the main inside club area was closed for a private party, so that blew, but this time it was open.
Inside: BEAUTIFUL decor, BEAUTIFUL lighting. I love the rich colors and gold. The chandelier is beautiful, and I love the gold female figures that point their boobies at you no matter where you're standing. It can definitely get a bit crowded in there, but it was fun to dance on the actual dance floor before heading outside. The bar was busy of course, but drinks were actually pretty strong for a club. Music was just ok.
Outside: The best part of this club. My girls and I were feet first in the pool in our hot dresses, dancing together with no one bugging us or poking their wieners at us. Yay for no weiner poking! Literally inside one of my friends had an awkward encounter with a boner. Overeager much?
The pool is stunning, the view of the Wynn is great and you can play table games also. They had a girl dancing with glowy things, which was fun to watch. People watching was also awesome. The lighting outside makes it much easier to spot the sloppy drunk hot messes. SO fun!