Two person setup sounds nice but it does have serious hardware requirements. I understand that sometime down the road for v3, iPi is hoping to support recording with multiple computers so maybe that will help.
In the meantime, I do my multi-character setups in separate passes. I find that if I have an audio track to perform to, especially with dialog or music and lyrics, it's fairly easy to synchronize actors. In the two cg '
Brudders' projects we have posted on Vimeo, that's how we handled our character interactions.
On a live action feature film I worked on last year, I needed to animate two soldiers interacting in the background. Soldier A was climbing out of a landing military helicopter and soldier B was waiting on the ground. Soldier A then opens the door of the helicopter, hops out and walks a few meters to shake the hand of soldier B, who also walks forward to meet Soldier A. In this case, I didn't bother with an audio track, I just counted off the time for when the handshake occurs in my head. Then, in Motion Builder, it was easy to slip the motions a few frames and reposition them to get the handshake in sync. The motion was captured in my living room early in the morning and I had it dropped into an animation scene at work by lunch time.
G.