I'd love to hear the about the decision process into the design and placement of the tabs for #IE9.  Mozilla hashed this out in a well thought out process and even posted a great video about why the changes were necessary.  Here is the link: http://blog.mozilla.com/faaborg/2010/06/24/why-tabs-are-on-top-in-firefox-4/

Why did the IE team decide to go in a different direction?