Wow this is cool... IMO the limiting factor in wide adoption of XPS was that it required the WinFX framework and that framework is only supported on WinXP (SP2), Windows Server 2003/R2, and Vista.
Today the XPS team have announced that the Beta 1 of the XML Paper Specification (XPS) Essentials Pack has been released!
"We built the Essentials Pack with an independent parser and renderer on Win32 platforms to provide XPS viewing on Windows 2000 and Windows systems without WinFX Runtime Components. This is a great validation that independent XPS implementations are possible."
Very Cool~ if you want to read more about XPS go here.