Wow! If these formats are truly open (colour me skeptic but I'd my skepticism to be unwarranted!), this is a win! Did Marc "Mr. Open Formats and Micro Content" Canter have anything to do with this?

From Brian Jones: Office XML Formats : New default XML formats in the next version of Office.:

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Open Format: These formats use XML and ZIP, and they will be fully documented. Anyone will be able to get the full specs on the formats and there will be a royalty free license for anyone that wants to work with the files.

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