Its a hot topic at the moment, especially amonst  our customers who are recieving desktops with Windows 7 OS and little resource to role them back to XP.  Microsoft are obviously saying you can do it legally (see recent blog listing ‘Can I downgrade‘) but in reality its proving an awkward excercise that most IT managers would rather not undertake.
So, should you be upgrading  your Server architecture?
This document is primarily for Application Developers, but offers IT Managers the heads-up on Win 7 OS and Server 2008 compatibility.
The document offers information on how to verify the compatibility of your applications with the new operating system and provides an overview of the few known application compatibility issues in Windows 7 and Windows Server 2008 R2. It also points out differences in performance, reliability, and usability, and provides links to detailed white papers and other developer guidance.
Windows 7 and Windows Server 2008 R2 Application Quality Cookbook:  A Developer’s Guide to Application Compatibility, Reliability, and Performance – [Read here]