How well do the new layout tags in HTML5 degrade? What are the hazards in using them? (I'm not talking about <video>--I've seen specific fallback code for it).
Specifically, in the case of something like
<html>
<head></head>
<body>
<header>
<h1>Talking Dogs</h1>
<b><p>Humans aren't the only talkers!</p></b>
</header>
<article>
<p>Ever encountered a talking dog? I have.</p>
<p>It all happened one day as I was walking down the street...</p>
</article>
<footer>
© 2009 Woofer Dog Corporation
</footer>
</body>
</html>
Would using <header>, <article>, or <footer> cause any browser problems? Do they degrade to <div> in unsupporting browsers automatically? Or if I include them, should I only include them for semantic meaning, and not for CSS styling or DOM scripting?