OpenXML and ODF - it's not a zero sum game.
Jean Goffinet of Clever Age has a post intriguingly titled "Are we traitors or mercenaries?" on the ODF Converter team blog describing a lunch appointment with two "emissaries" from OpenOffice.org and OASIS. He explains how after the project was announced he reached out to both organisations, as he says :-
After the project launching, I had contacted both organizations: the first one to ask for contributors (our plug-in is designed to allow its use by other applications, so we thought that OpenOffice.org could be interested in joining the team to make its product open and save docx files) and the second to have its agreement to use OASIS logo in our plug-in (agreement that we never had, so we decided to use another picture).
Sadly he then goes on to say
The two emissaries wanted to tell us how we were seen by OpenOffice.org and OASIS, and also to ask us some questions regarding our position. So we learnt that the OpenOffice.org team considered us as "traitors" (who are those traitors that work for the Big Satan Microsoft?) and that people from OASIS "did not like us" (even if they don't really care about our little company). In fact that was not a definitive judgement: they wanted to know exactly in which camp we were - because in this war, you cannot remain independant, you have to choose your side. So by default, as we work for Microsoft, we are seen as enemies; but if we show good willing and for instance join the OpenDocument consortium, that could be a sign that we may on the contrary be friends.
If you are interested in document formats, in OpenXML, ODF, or interoperability you should read the rest of his post. For my part I don't think that this is a zero sum game. Happily more and more of the policy makers I am interacting with are reaching this same realisation too.