Hakkasan Sunday, XS Monday, Hyde Tuesday...They all were cool in their own way. Hyde was a diverse crowd, and it is crowded and small, the music was a good mix of current and older music, small dance floor, but awesome view of the fountains. I don't think it would be as much fun without bottle service and your own area. I heard it was $9 for a beer and $36 for most top shelf drinks, so bottle service is the way to go.
Also, forgot about the Voodoo Lounge. Just an incredible view of Vegas. It was cooler that night, so not too busy. But a very cool place, big service sections as well...
XS is great as well, the pool area is very nice, you can't go wrong with either.