And you don't even have to sacrifice the new user interface for the old one. Classic Menu inserts a new ribbon at the extreme left edge of the Office 2007 interface. This new ribbon contains both the old, familiar menus and the old, familiar toolbars; click it and you're back in Office 2003--but with 2007's features. And you can always click on one of the other ribbons to return to a more modern Office.
Vendor Addintools offers several similar programs. There are separate Classic Menu programs for each Office 2010 SKU (, , , and so on). If you're short on cash and only want the old-fashioned interface for a single application, you can buy cheaper Classic Menu add-ins for , , and other Office applications -- either for version 2007 or 2010.