I hooked up a third airport express to my network and tried out the multiple stream AirTunes. I’m happy to report that it does indeed work. We let iTunes play for a few hours sending the audio out to the computer’s speakers as well as two Airport Express units over the wireless network. The music is synchronized very well and while standing in between two different rooms with streams playing (one over the network and the other local on the computer) it sounded good with no signs of time phasing. I plan to hook two more Airport Express units into the network and attempt to send music to 5 separate sets of speakers at once. Stay tuned!