The 451 Group analysts Matthew Aslett, John Abbott, Nick Selby, and Vishwanath Venugopalan listed the potential winners and losers as part of their analysis of Microsoft's API and protocol announcement.
SAMBA - Proper interoperability with Windows File and Print services without having to guess the APIs. (Note: Samba struck a paid interoperability deal with Microsoft in December).
Vendors wanting to get their client software interoperable with Exchange
Exchange alternatives -- Zimbra, etc. Enables them to develop proper interoperability with Exchange servers and the ability to act as a replacement for Exchange.
Calendar and Workflow clients - Vendors will be able to build proper hooks into Exchange.
Vendors and end-users looking to implement Web services and software-as-a service architectures, who require deeper and more consistent access than has sometimes been available from Microsoft.
Losers...Google -- as an open platform advocate -- and Linux-focused vendors such as Red Hat and Novell may find themselves less able to play the "proprietary" card against Microsoft in the future.
Any company attempting to sell hub workflow servers that competes directly with Exchange and SharePoint. They might have to implement Microsoft protocols, but on the other hand, they can still offer interoperability.
Any companies whose secret sauce involved reverse engineering MS APIs.