I thought Microsoft had forgotten about Mac users, but it seems like Office will be receiving a much needed update. Office 2007 for Mac will borrow heavily from the Beta released for PC users a few months back. A main feature of Office 12 will be the Ribbon which is sort of like a launcher to doing various tasks in Office, rather than hunting through menus.
Also, files will begin using an XML format which is slowly becoming standard. But the #1 reason all Office-using Mac users should upgrade to Office 2007 - it's a universal binary and will fly on your latest machine. Expect to shell out big bucks for Office 2007 when it hits computer store shelves 3rd quarter of 2007. APC magazine has the rest.