Microsoft is of course still working on getting their OOXML format accepted as an open standarda at ISO. I'm of the opinion that it should never be accepted and this article is another in a long row of articles that explains why: THE DEPRECATED “SMOKE SCREEN” OF MS OFFICE OPEN XML (OOXML)
Here is a quote:
Launch Microsoft Office and try to save a file in the format specified by the draft standard at ISO. You can’t. There is no compatibility mode in Microsoft Office that limits input to the feature set specified in the official Microsoft Office Open XML draft ISO standard. Any suggestions of interoperability for anyone wanting to support the Microsoft Office Open XML specification is ridiculous, especially since Microsoft itself won’t allow its customers to write to that format.