Only time will tell whether OpenXPS will succeed where the plain vanilla XPS document format has failed, namely to erode the domination of Adobe’s Portable Document Format (PDF).

The Open XML Paper Specification, or OpenXPS for short, is a new document file format supported in Windows 8 Developer Preview Build 8102 Milestone 3 (M3).

I think it’s rather safe to assume that the RTM Build of Windows 8, or whatever it will be called after the platform goes gold, will also play nice by default with OpenXPS.

Windows 8 OpenXPS, the Latest PDF Killer - Softpedia

That sounds good, but will take some time until it reaches the popularity of PDF.

I have been using XPS documents for a few years now. They are fantastic. ​Better than PDF in my opinion. They're native to Windows and easily usable just about anywhere.