At GA-PCOM, I was interviewed by two people at the same time, and one guy did most of the talking. It was super-easy.
I can't imagine they do it differently at regular PCOM, but I guess they might.
The only interview experience that I would describe as a "panel" was EVMS, and that sucked. It didn't have anything to do with the number of people. It had to do with the fact that they had **** for brains.