The change is effective immediately, affecting all current GFW Live titles (such as Halo 2 and Shadowrun) as well as future releases. MS is also set to expand the service through a GFW Live Marketplace, due this fall. Like the XBL Marketplace, the PC-centric store will offer free and paid downloadable content, demos, and trailers (is this PC Live Arcade?)
In addition to these announcements, MS is working to make the GFW Live interface "much more PC friendly" (read: not like the Xbox 360's now deprecated "Blades" interface) along with reducing the technical requirements for developers. One criticism of the interface from the development camp has been that it must be built into every GFW title, rather than a stand-alone client such as Steam.