Rick Jelliffe has posted some thoughts from his initial review of the Open XML comments that were submitted by the various national standards bodies during the technical ballot phase of the process.
The bottom line: there are a few touchstone issues that may be tricky but it is difficult to see from the comments that DIS 29500 would not be successfully fixed and approved to be an ISO standard. The particular touchstone issues I see are that spreadsheet dates need to be able to go before 1900, that DEVMODE issues need to be worked through more, that the retirement of VML needs to be handled now, and that there needs to be a better story for MathML.
He has makes some interesting observations around the comments that were put forwards.
If any of you are aware of any similar analysis that has taken place and is posted publically please drop me a link.