Office 2007 ODF - UOF Support
You can check them at:
What I wasn't aware of, is the study to merge both formats. I can extract some text from the article:
One reason has to do with the formats' allocation of their respective namespaces. The Lab described the UOF schema as being much more structured, replete, and flexible, while certain parts of the ODF schema seem more arbitrary.
You can check the announcement at http://www.microsoft.com/presspass/press/2007/may07/05-20UOFODFPR.mspx?rss_fdn=Press%20Releases