This year’s Microsoft lucky number is 7. If using Windows 7 and (waiting for your own) Windows Phone 7, you should also take a look at Internet Explorer 9 Platform Preview 7.
After the release of Internet Explorer 9 beta on 15th of September 2010, Microsoft keeps us up to date with new releases of technical platform previews of new browser with several cutting edge technology improvements like HTML5, CSS3, GPU accelerated rendering using Direct2D and DirectWrite, ClearType Web Open Font Format, faster Chakra Engine for JavaScript, SVG support and cleaner, simpler design.
Since beta release, platform preview 6 introduced support for CSS3 2D transforms and HTML5 semantic elements, and in the latest, 7th, speeded up Chakra engine sky high in comparison to other browsers.
More on IE blog: http://blogs.msdn.com/b/ie/archive/2010/11/17/html5-and-real-world-site-performance-seventh-ie9-platform-preview-available-for-developers.aspx
Test drive: http://ie.microsoft.com/testdrive/
Internet Explorer 9 Beta Guide for Developers: http://msdn.microsoft.com/en-us/ie/ff468705.aspx