My girlfriend and I came to check out the new science centre in January for an adults only night. The theme of the night was "Find a new hobby". It was pretty great.
In the main hall they invited local clubs to come set up shop and show everyone what they were about. There was stamp collecting, R/C vehicles, chess, and Lego among others. Most importantly, there was a cash bar. Though you couldn't go into the exhibit areas with your beverage (damn spilly talkers ruining things for the rest of us), you could wander through the main hall and chat with the different clubs while you sipped away.
From what I could tell the vast majority of regular exhibits were open. Even the younger kids area. The tree house/fort was full of people running around in their socked feet. I would argue that this area was the best part next to the booze.
If I'm ever in town again when an adults-only night is happening I'm definitely going to make an effort to visit again.