It seems to me that ember.js is a better approach to this - much cleaner application model and richer data support with routing and view state.
That said, I'm with you broadly on Javascript+HTML5 on the desktop. Actually just wrote something up around my thoughts on how to do this with Ember.js if folks are interested:
The tech is different but the purpose is the same - to give a great application experience with software written in JS/html/css, on every platform with a single codebase. Ember is betting on the browser to be the runtime, appjs is writing their own.
That said, I'm with you broadly on Javascript+HTML5 on the desktop. Actually just wrote something up around my thoughts on how to do this with Ember.js if folks are interested:
http://bit.ly/LybVgo