Joel Spolsky (one of my favorite tech writers) has this beautiful analogy in response to standards:
"If you’ve ever visited the ultra-orthodox Jewish communities of Jerusalem, all of whom agree in complete and utter adherence to every iota of Jewish law, you will discover that despite general agreement on what constitutes kosher food, that you will not find a rabbi from one ultra-orthodox community who is willing to eat at the home of a rabbi from a different ultra-orthodox community. And the web designers are discovering what the Jews of Mea Shearim have known for decades: just because you all agree to follow one book doesn’t ensure compatibility, because the laws are so complex and complicated and convoluted that it’s almost impossible to understand them all well enough to avoid traps and landmines, and you’re safer just asking for the fruit plate."

Although he wasn't speaking about OOXML, I think his arguments will apply. Read the full article here: http://www.joelonsoftware.com/items/2008/03/17.html