Doug Mahugh blogs about Office 2004 for mac support for Office 2007 file formats.
Office for the Mac hasn't shipped with Open XML support yet (but it's coming soon). So if you're a Mac user in an organization that has moved to Office 2007 and the Open XML formats, you might want to check out Panergy's docxConvertor tool.
It's a stand-alone convertor that translates "docx" Open XML documents into RTF. Most commonly used formatting and features are translated, including styles, headers/footers, comments, theme settings, and more. See the features list for more info.