This is probably my favorite place in Station Square. Zen is a trendy place, that's well aware of its place within the upper echelon (such as it is) of Pittsburgh dance clubs.
It's a huge space, low-lit with a couple pretty huge bars so it's easy to get a drink. If you want to get bottle-service it's not difficult to secure. The crowd is well-dressed; you're not going to find kids in cargo shorts. The male:female ratio isn't always right but the crowd itself is relatively diverse.
The main dance floor gets pretty packed towards the middle and end of the night. Like most places in Pittsburgh, the music selection isn't exactly cutting-edge. It's standard top-40 and yes, you will also probably hear MJ a few times during the night. (Not that I don't love me some Billie Jean).