OpenOffice makes great strides to be compatible with Microsoft formats, which is often an uphill battle with how often MS changes their formats around. With how intent MS has seemed to be in the past on keeping outsiders from prying into an Office document, it is surprising now that they claim to be opening up their office suite to the ODF format. Microsoft claims that their current and future versions of Office will support the Open Document Format version 1.1, starting with Office 2007 Service Pack 2. They also claim they are joining OASIS to work on the next release of ODF.
The first part might be hard to swallow but at least plausible to supporters of ODF, but Microsoft being part of the decision making process in future versions of ODF sounds bad. Their tactics in the past of embrace, extend and obliterate has let them remove many competitors in the past, and given how big of a cash cow is Office is to them, it is easy to see why many are skeptical.