I was disappointed with Late Night. Basically, in my opinion, the only fun feature of the EP are the vampires. I hardly ever visit the clubs because my sim can't go to their open hours without falling over from exhaustion after working all day.
Also, living in an apartment isn't fun, the celebrity status is annoying because you can't be friends with everyone until you raise your star power, and a glitch where NPCs mob a lot is really beginning to make me mad.
Due to this EP, guests who come to my sims' parties leave immediately after they arrive and I can never have a good party.
I love the vampires, but if you don't have Generations or Ambitions yet, buy those instead of Late Night.