Ok, so this stuff is really cool and when I first started playing around with 'Springfield' and Silverlight I guess I was in heaven :) But... as a control vendor I think we will live in the Silverlight 1.1 world. Silverlight with JavaScript is cool but the fact that it is not compiled and people get to see our code is less then a warm fuzzy... But business asside, Popfly is really really cool and what this really does it provide awesome dev tools for the non dev/designer. Now on some ones web site or blog or whatever and using Popfly they can slam together a mashup right quick. For example if I'm a designer of say cloths and we have a blog we can take pictures of new designs each week and have some slide mashup show the latest and greatest from our photoshare place and no one has todo any fancy coding.
For the power user non dev time popfly is a godsend. http://www.popfly.ms/Overview/