This looks really great. Only problem I see is the lack of support for IE 6 and 7, and it seems they won't be in the future. Anybody knows why that is?
The Persona cross-browser support shim needs window.postMessage and the HTML5 storage APIs, which IE 7 doesn't have. Working around it didn't seem worth the security and maintainability cost to the codebase, nor the opportunity cost over working on other features.
