I still give XS 5 stars because it is a great nightclub; however, I'm not as in love with it as I used to be. To me, XS is more of a music venue than a dance club now. Seems like every weekend they feature some house DJ, which is fine but it makes the dance floor more like a concert floor. The bigger the DJ name, the more crowded the floor gets, making it a lot more difficult to dance.
"Sunday Night Swim" - in the summer you can wear your bathing suit to the club and swim in the pool. Expect house music and a smaller crowd. During the summer, they close the inside dance floor, so everything is outdoors. I would definitely recommend wearing a bathing suit under your club attire if you choose to go to XS for Sunday Night Swim. They throw little inner tubes into the pool so you can float around - pretty fun.
Other nights, even without a big EDM headliner, XS is still mostly house music with maybe an hour max of hip-hop and top-40 later in the evening. The atmosphere is definitely still fun and lively, but the homogeneity of the music just doesn't make me want to dance all night. Marquee gets a lot of EDM headliners too, but at least they have multiple dance floors with different music. XS is not so much a dance club for me anymore, but more of a place to hang out with friends, drink, gamble, and maybe splash around in the pool. I used to be able to stay at XS past 4am in the morning, but lately I find myself leaving by 2am. I still always have a good time, but it's just a different experience.
(Side note: I must say though, the music is poppin whenever they have celebrity guests, such as a rapper or hip-hop artist, visiting.)
Overall, I do recommend that anyone going to Vegas for the first time try out XS at least once. They have awesome table service, good VIP hosts, a beautiful venue, and most importantly, a quintessentially Vegas atmosphere: excess.