Windows 7 is packed with lots of new “developer” or “platform” features.
We are confident most customers would benefit (better per, better UX) from running on Windows 7; but we also acknowledge that adopting a new OS is not always immediate (specially for any large enterprise that recently rolled out Windows Vista).
For developers whose customers can’t move to Windows 7 immediately, Microsoft recently announced the “Platform update for Windows Vista” beta.
The Platform Update for Windows Vista, brings a lot of the Windows 7 goodness into previous OSes (Windows Vista and Windows Server 2008); the update includes Direct2D, Direct3D, DirectCompute, Windows Imaging Component (WIC), DirectWrite, XPS , and the Windows Ribbon) .
You can learn a lot more about the Platform Update here.