I can’t help but assume that Microsoft is adopting XML as the default file format, not because they love open and interoperable formats, but because OpenOffice has received Oasis certification of their open and interoperable XML formats already.
I think it’s good that Microsoft feels threatened. I think it’s bad that they are offering their XML schemas with “royalty free licenses” to all and sundry, because that just encourages further lock-in to MS products. We’ll see how it plays out, I suppose.