I just blogged about the AJAX navigation feature we added to IE8 which will greatly help providing a better AJAX experience with respect to navigation. Remember those frustrating moments when you want to share the web address of the page you are seeing in the maps or the home on redfin.com and your friend gets the first/unrelated page? This will hopefully help web developers fix it in the future.
http://blogs.msdn.com/ie/archive/2008/07/14/ie8-ajax-navigation.aspx