A handy summary
There is a lot more to this than just support for ODF in the Microsoft Office product, although obviously the native support for ODF is a focus for many of the words that have been written overnight.
The company also announced plans to offer greater support for a number of alternative document formats - including Open Document Format (ODF) v1.1, Adobe Portable Document Format (PDF) 1.5, PDF/A and XML Paper Specification (XPS) - within Word 2007, Excel 2007 and PowerPoint 2007.
In addition, Microsoft will support the future maintenance and evolution of these format standards by participating on the standards committees charged with these activities. This means that Microsoft folks will join the OASIS ODF TC and participate alongside IBM, Sun, Novell and everybody else present.
Finally ODF will be added to the list of specifications that are covered by the Open Specification Promise, ensuring that every developer has access to any intellectual property that Microsoft might put forwards during these maintenance processes.