Humorous quote over at the hacker news thread on the previous post:
This complaint is as old as the hills. You may as well slap an obnoxious "Designed for HTML5" button on your site. The cost of having the world's largest addressable audience of any development platform is that web developers have to deal with the fact that it varies a lot. Them's the breaks.
Edit: because I hate comments that are purely negative, my suggestion for getting users to the latest technologies is to use libraries (like YUI and jQuery) which do the hard work of implementing newer features in backwards compatible ways, but use the modern feature if it's available...
Wish I'd thought of it earlier.