A number of people have asked where to get software to view XPS Documents. The XPS Viewer allows you to view XPS Documents, and will be included in the WinFX Runtime Components and Windows Vista. Details on how to install the latest WinFX Community Technology Preview (CTP) are available on the official XPS site.
Installing the WinFX CTP gets you the XPS Viewer and the APIs to create your own XPS Documents programmatically via the WinFX APIs. For those installing the next Windows Vista CTP, you should also have access to the Microsoft XPS Document Writer (MXDW), which will allow you to print from any application to the MXDW print driver to generate an XPS Document.