Microsoft released IE9 beta, you can download it at the company's Beauty of the Web. A list of all the new features can be found at IEBlog.
The IE9 experience starts from what people use regularly for launching tasks and managing windows. While consumers have browsed with a home button and bookmarks (or Favorites) for fifteen years, and tabs for closer to five, they use the parts of Windows 7 for launching tasks and managing windows far more. More people launch a pinned application from the Windows 7 taskbar (87%) than use the keyboard shortcut (ctrl+T) for opening a new tab. More people pin at least one non-default application to the Windows 7 taskbar (33%) than add a link to the Favorites bar. While tabs are central to the browsing experience, over 97% of IE sessions have 5 or fewer tabs, and more than 90% of users have never had more than 8 tabs open at once. The set of real-world usage data represents hundreds of millions of sessions and tens of millions of users worldwide, including students, enthusiasts, developers, people at work, and consumers in general. This post from the E7 blog has good background on the use of data to inform product design..