Ed Banti has blogged some information about Exchange Server 2007 and Windows Server 2003 SP2.
If you haven't heard, Service Pack 2 for Windows Server 2003 is now available. In the final few months leading up to the RTM of Exchange 2007, we performed automated testing of Exchange 2007 with Windows 2003 SP2. Once Exchange 2007 was RTM, we continued to test. Service Pack 2 for Windows 2003 provides additional language support for Exchange 2007. In addition, you'll also find that the installation experience of Exchange 2007 is more streamlined because many of the updates that are required for Exchange 2007 (for example, Microsoft Management Console 3.0) are built into SP2; as a result, you don't need to download and install these individual components. And of course, administrators will have the benefit of running the latest version of Windows Server 2003 to ensure their system is fully patched and up-to-date.
Read at source: http://msexchangeteam.com/archive/2007/04/10/437637.aspx