Here is an interesting article that is touching to an issue that was mentioned several times in the discussions around OOXML: Microsoft won't accept any changes that is not compatible with their 'already shipped' Office 2007:
This reminds me of an exchange of email during the efforts by Microsoft to standardize the file sharing protocol that Samba implements (CIFS). After a white paper was published demonstrating a man-in-the-middle security attack against the current protocol Microsoft responded by publishing a specification for cryptographically signing the packet exchange. This change fixed the security hole and was a good first response to the attack. Unfortunately, after analysis by some of the experts on the list we discovered that there were some theoretical holes to the new signing protocol, which needed a few trivial changes in order to fix and improve the security. After these proposals were submitted, the response came back from Microsoft that although the fixes were valid, unfortunately the code was already written and was going to be shipped in the next service pack. End of discussion. It wasn't even in a shipping product yet, but the specification was determined to be unchangeable as they didn't want to change their existing code.
Let's bet on the fact that Microsoft/ECMA will propose changes that will look like this:
We don't correct the NetworkDays() function in order to add support for Muslim countries, but we flag it as deprecrated, and we create another one named NetworkDays2() that has the support for this feature. The right thing would be to correct the function, not to create a new one. I take the bets on this one.