A representative of the W3C says it’s too early to start using HTML5. Scott Gilbertson of WebMonkey argues to the contrary. Given the pace at which Internet Explorer users upgrade, if you are opposed to using HTML5 now, you’ll probably still be opposed to it a decade from now:
The fact is HTML5 is here and you can use it today, you just need to use shims, fallbacks and workarounds for older browsers. Yes, that’s unfortunate, but that situation isn’t going to change any time soon. If IE8 — which lacks support for most of HTML5’s features — has even half the longevity of IE6, we’ll still need fallbacks even when 2022 rolls around and HTML5 is, in the W3C’s opinion, finally ready.
Obviously we can’t just migrate to HTML5 wholesale yet (unless we’re creating Web sites optimized for iOS and Android), but the time to weigh whether using HTML5 and compensating for old browsers makes more sense than using older techniques that work in all browsers has arrived.