Millions of people are already using a hosted service powered by an early version of Exchange 14, although the server version won't come out until next year. The last time with Exchange 2007, though, Microsoft built the server software first and then delivered the service. In developing Exchange 14--and indeed many components of the next Office--Microsoft has flipped the switch and is instead developing the service first and doing the server work second. By doing the service first, Microsoft is able to create a large base of testers early on.

Full Article