In case you missed Keith's announcement...Spring Web Flow PR2 is now available with such cool features and OGNL-based conditional transitions and portlet support. And the big surprise is that it also has continuation support!
This is big news. I recall last year when Glenn Vanderburg and I shared a SuperShuttle to the airport and he was describing the idea of continuations (in short, the ability to develop a web application as if the client were "local" to the application...in effect putting the application on hold while awaiting for user interacton and then picking back up where you left off once the user responds). I remember thinking it was a cool idea, but would it ever become a reality. Apparently, now it has with Spring Web Flow PR2.