The main use of the Lounge is when a flirt goes out of hand in #Elliquiy, the involved participants can move it to the Lounge, since there's no PG-13 limit there. It's as active as people make it to be.
Keep in mind though, that Ellounge has a basic setting, a living room (though very lenient on details), and anyone who hops into the channel, hops into the virtual room as well and can interact with whatever's already going on.
If you want to RP in your own setting, you'll have to set up something privately. Call me on IRC (just mention my name to let my computer play a sound) and if I'm around, I can help you out on making such a channel.
As mentioned, the /list command shows a list of channels, and there are some decent ones. However, those usually involve everyone participating to be part of a greater setting. It seems to be the only decently working setup, as settingfree rooms are just the crappy cyber channels.