The Adobe Portable Document Format (PDF) has become the de facto standard for document interchange. Now Microsoft is quietly challenging that standard with its XML Paper Specification.
Here's the key: XPS is an integral part of Windows Vista. Any software program running in Vista can create a document in the XPS format simply by printing. Microsoft has also created free XPS writers and readers for Windows XP and Windows Server 2003 (details).
Will XPS succeed? An excellent ComputerWorld article includes some interesting history about Microsoft's earlier attempt at this sort of printing standardization, the Windows Printing System. I was extremely impressed with WPS and used it for many years with my HP LaserJet II (and it was a sad day when that printer died and took WPS with it). It was very clear to me that Microsoft knew what it was doing then. XPS is far more sophisticated and, unlike WPS, is platform-independent.
I believe XPS will become a force to reckon with. If you are using Vista now, give it a whirl. Expect to see XPS-compatible printers soon. And pay attention - XPS will be a hot topic of technical conversation for the next couple of years.