Microsoft have announced official support for the Microsoft Office Communications Server 2007 R2 member server role on a server that has a Windows Server 2008 R2 operating system installed. Now for the fine print.. the following scenarios are currently not supported on Windows Server 2008 R2:

• Group Chat will not function in a Windows 2008 R2 forest or when Group Chat member servers are joined to a Windows 2008 R2 domain. Some issues with changes in Windows 2008 R2 require a Group Chat Client and Group Chat Admin Tools hotfix, scheduled for mid-April 2010.
• Deploying Group Chat on Windows 2008 R2 is currently not supported.
• Upgrading the operating system to Windows Server 2008 R2 for an existing installation of OCS 2007 R2 is not supported.
• Installing 32-bit OCS 2007 R2 administration tools on 64-bit Windows 2008 R2 is not supported.Development with Speech Server 2007 Developer Edition and deployment of the Speech Server 2007 role are not supported on Windows Server 2008 R2.

For more information, see KB 982021