Not much progress going from one non-html5-compliant browser to another. It still means everyone's stuck having to support flash and other proprietary plugins. IE9 at least allows us to move forward with modern standards.
It is not just new stuff like HTML5. XHTML 1.0 is already 11 years old and is not supported in IE8, forcing it to be served using the HTML MIME type and parsed as HTML. Often XHTML served this way becomes invalid even if it was originally valid. I wrote an article on Reddit about this.
