It seems the cardspace team has been at work simplifying the user experience for Cardspace prompts. See codename "Geneva". This looks pretty good; they've even included the new Geneva server for creating managed cards, which is something I'd like to explore at some point. I'm very curious what work if any has been done to integrate OpenID in conjunction with cardspace.
I'm not sure just how far Cardspace is penetrating, as I've yet to run across a site (aside from Windows Live, and even that's in beta, and has been since at least August of 2007!), which actually uses cardspace for authentication. I have found many articles from the 2006/2007 timeframe purporting firefox 3.0 support of cardspace, however the plugins online don't show them. Windows live login requires IE to even attempt a cardspace login.