I'm sorry, Stephen, but the facts are: "The [OOXML] format was initially standardised by Ecma (as
ECMA-376) and, in later versions, by ISO and IEC (as
ISO/IEC 29500)."
- http://en.wikipedia.org/wiki/OOXML
Since this question was first posed, LibreOffice version 4 has been released. This newer version of LibreOffice has better support for OOXML than version 3, but LibreOffice still doesn't default to the standard OOXML open standard and hangs onto the obsolete
ODF format for reliability purposes. Converting core OpenOffice code to work with the new file standard is a gargantuan task that has yet to be implmented by open source advocates. On the plus side, retaining the old code base gives LibreOffice the ability
to open files that were saved in file formats Microsoft has abandonded and save them in the up to date OOXML file format.