Not sure if this is the right place, but I've made a little screencast of what Stack Overflow looks like when it uses the HTML5 History API: http://vimeo.com/22396598
You can try it out yourself by using the following bookmark: https://gist.github.com/919358
For a little background info. Currently the Stack Exchange sites do not use the HTML5 History API and use the HTML4 hashchange functionality on the user profiles. Hashes are not ideal as they cause double loads when initially loading a page with a hashed url, are not acessible by js-disabled users and search engines, and cause duplicate urls for the same content. The HTML5 History API solves these problems by allowing you to modify the URL directly. More info.
So what do you think? Is this an improvement that the Stack Exchange team would be willing to look into?