NiXPS is a Belgium-based company "dedicated to developing cross platform applications and technology for the XPS document format". Today they announced the release of NiXPS v1.0 that provides XPS manipulation and inspection for both Mac OS X and Windows. More info in their press release.
Also of interest is that Artwork Systems has made an investment in NiXPS. Artwork Systems Group includes Enfocus, a company that provides pre-flight and other workflow solutions to end users and technology partners in the design, printing and publishing industries. More details in Artwork Systems financial press release.