I’m not a huge expert - I’ve just read a couple blog posts about the UI design process. However, all the commands are in the ribbons or accessible by the ribbon, so they must have worked it out somehow. Just playing around with Word 2007 myself, there’s eight different tabs on the ribbon for major groupings of commands (Home, Insert, Page Layout, References, Mailing, Review, View, Add-Ins), and some of the buttons open a dialog box. Also, some tabs only appear when needed (e.g. insert a picture or select a picture and the “Picture Tools Format” tab appears, insert a table and the “Table Tools Design” and “Table Tools Layout” tabs appear).
But all the commands fit in the somehow, and every command has one home and is in the same place. My understanding is that in previous versions of Word some commands were in the menus and toolbars, some were only available from toolbars, and some were only in task panes. Then in some later versions of Word the menus tried to be “smart” and hide the less commonly used tasks, but I always found it to be a huge pain in the ass when trying to find a command you hadn’t used in a while.
I’m not some huge Office 2007 devotee or anything, but after fiddling around with it for the last year (came on my new laptop I got for school), I don’t have any huge issues with it. I am somewhat of a power user, and in old versions of Word I customized the hell out of Word and added custom macros, toolbars, etc… and use mostly keyboard shortcuts. I’m not finding the lack of user UI customizability in 2007 to be a huge issue for me, and the Ribbon works fairly well overall.

