To be honest, I think the browser support picture is changing. An increasing number of people are developing apps where they have some idea of what their target

To be honest, I think the browser support picture is changing. An increasing number of people are developing apps where they have some idea of what their target audience is like. Greater than 40% of the browsing public is now using Firefox, Chrome or Safari. Flexbox is already in that bundle of browsers (and it rocks :) calc is in IE9+ and Firefox. Chrome and Firefox are in autoupdating very short release cycles (or, at least, Firefox is getting there rapidly). I think the ideas in HSS are interesting, and I understand the motivation. But, the world is rapidly changing. Not everyone is going to be able to support the latest standards in their apps, but I think we're moving past the point where most developers will need to support a 10 year old browser. Time will tell! (obDisclaimer: I'm a Mozillian)