This place is really nice. I feel seriously spoiled when I try to go out in SF or in Sacramento because nothing I've been to seems to even come close to topping XS.
XS's biggest and best feature is its size. Plus the entrance (as you approach the opening of the interior of the club) is really really impressive, especially since it opens out into the pool area and expands around it into a pennisula around the pool.
However, I went during memorial day weekend and the place was PACKED. I've never seen it so busy there and was a bit of a turn off that it was so packed inside. I went on sunday (not saturday, saturday was stupid crazy and the cover was ridiculous; plus we got in for free on sunday). I think Keri Hilson was there singing her songs but she sounded so off I think the they told her to stop performing (?)
Also the music there tends to vary a lot, if you're used to listening to hip hop/ pop music at a club, XS will do that but on occasion it'll do a quick switch to some house music and totally throw most people off guard.