Microsoft's Office for Mac team blog wrote about their thought process in developing the user interface for the upcoming Mac Office 2008.
Mac users have strong expectations about their user interface. We're often told by our users that they definitely want us to look Mac-like. .... We could have just left the Apple and app menu in place, and ignored the rest of it. Not only is this a waste of screen real estate, it breaks the user's mental model. But the Ribbon does some great things, and we want to capitalise on their innovation while still ensuring that we keep a Mac-like experience.
They've also posted a sneak peak of Mac Office 2008 at http://www.macoffice2008.com/
