About 80% of the people we invited and were either "yes" or "maybe" responses to the RSVP showed up -- which is a pretty good ratio I'd say. So, we had 20 people in the house at the high water mark (including the hosts).
The invitees were from various spheres in our lives: Former Swinger Connections, Craigslist Connection, OKcupid Connections, LoveTribe Connections, and Polyamory Discussion Group Connections. Together they make a great mix of people who generally seemed to get along pretty darn well! (Some in a more intimate fashion than others...) ;)
The setup: DOWNSTAIRS was the general social and food space. I really enjoyed how we re-configured the kitchen area for the bar and food tables. We were able to comfortably fill the downstairs kitchen/family room area with all of our guests. UPSTAIRS was the sensual spaces and I hung signs renaming each room: Guest bedroom became "The Torture Chamber" (containing the violet wand and B's custom strap-and-buckle chair), S1m0n's room became "The Stud Stable" (containing the Sybian), PolyGestalt and PolyFulcrum's room became "The Gallery of Delights" (as a public play and gathering space), PolyGestalt's office/retreat became "The Love Nest" (the only closed-door private place space for two or three people at a time).
The only odd thing for me was having so many of my actual and potential female connections in the same place at the same time. It was nice to be able to introduce them to each other, but at least a bit mentally awkward to balance enough interaction time between all of them. I mostly just "went with the flow" and roamed around the party making sure that everyone was having a good time.
So, from my impromptu exit polling when people left the party, I'd say that we have a repeatable party on our hands! The only question is: Should we have these every 3 months or every 6 months? Feel free to respond with your votes!