I hosted one for DH's birthday a few years ago. My biggest mistake was having too big of a party - if/when we do it again, we'll only 4-5 couples that know each other well. Since it was a varied group, and not everyone knew each other, some people felt a little awkward when the story forced more interaction.
You also have to be sure that everyone attends. One couple got stuck with a no-show babysitter and were VERY late and we couldn't start without their characters. Again, a smaller group would help with that.
Overall, it was a lot of fun and something new/different than the typical meet and greet dinner party.