I always build my applications with the philosophy of progressive enhancement.
You can use something like YUI History, history.js and loads of other state management scripts to maintain state across your application.
In HTML4 browsers, you would see something like
http://site.com/#/page/to/whatever and in HTML5 browsers, you will see something like
http://site.com/page/to/whatever, but it does not refresh the whole page.
So the conclusion: