If you don't approve OOXML, Microsoft will walk away, and you'll never hear from them again. Forget the fact that OOXML is already an Ecma standard (Ecma-376), and cannot be taken away. Forget the fact that Microsoft has other formats lined up for ISO approval in the near future, like XPS or HD Photo. Microsoft wants you to think that if you don't give them exactly what they want, now, they will walk away from ISO and you will be the worse from it.