I installed the OS X DigitalMe selector and the Firefox plugin (the browser is an intermediary in process of delivering cards to Web sites), created a self-signed card and went off and tested. It worked great. Finally a native InfoCard selector I can use for demos! Who knows--it might even prove useful in real work.
As an aside, there's a Linux version of the selector available as well for the Linux fans. If you use Vista, you already have it. If you use XP you need to install the .NET3 Framwork to get CardSpace working on your machine.
Kim Cameron, Microsoft's Chief Identity Architect, is excited about this as well. After all, this is an important part of his vision for InfoCards being ubiquitously available and used.