>The move to "web-page-apps" is not about eye candy, it's about speed, responsiveness and yes, usability
No, it is about following fads, just as web development has always done. Creating sites that are slower, less responsive, and offer terrible usability is clearly not done for reasons of speed, responsiveness and usability. Enhancing a page with javascript can increase responsiveness and usability. Replacing the page with javascript is moronic.