Hands down my favorite club in Vegas this trip. Hakkasan is off the chain. After you get through the 1304934 bouncers outside, make sure to go straight up to the top floor. This is where you'll find colorful flashing lights and be swept along in pumping music that blasts right through you and makes you feel like you're finally living that Vegas night life dream. It was crowded but not aggressively so (so you could still keep your little space in the sea of people without getting trampled). They also release streams of cold air once in a while, which keeps things interesting and cool (both literally and figuratively).
There's also a downstairs dance floor but it's so much more lame compared to the top. Don't even bother as it's a completely different vibe.