MSDN has released a guide on how to harness the power of P2P in Windows Vista for developers. Microsoft P2P solution intends to reduce the barriers that are common to traditional P2P applications.
Traditionally, challenges to P2P application development have included the need to develop proprietary protocols for message exchange, having to locate and connect with instances of an application that are hidden behind a Network Address Translation (NAT) or a firewall, and the need to support the inevitable infrastructure required to locate applications in a wide-area network (WAN). These challenges, while surmountable, have represented a substantial barrier, and as a result, many of us never consider the amazing collaborative functionality P2P applications provide.