If you want to use these new elements but are afraid of them not working there is a simple plug-in that will add these elements to old versions of CSS. I have viewed my new pages in an older browser only to find that the new elements are completely ignored, leaving my content without style!

Here is a temporary solution until the world catches up with us:
http://code.google.com/p/html5shim/

It's a little JavaScript file that you include in your header. It puts all of the new HTML5 elements in to the CSS table so that your code can be loaded in to them just like they were "classes" or "IDs".
The example given has an lte IE9 hack on it but you can use this code for all of the older browsers. I have tested it and it works as advertised.

So go forth and code without fear of disgraceful degredation.