Free Software Magazine has an article entitled ODF/OOXML technical white paper, a white paper based on a technical comparison between the ODF and OOXML formats. (The author's original paper is also available as PDF and as ODT, both a bit easier to read). ODF is the Open Document format for office documents created by OASIS, whereas OOXML is Microsoft's implementation of Open Office XML. These formats are quite different, and the article illustrates a number of differences. Unfortunately the two formats don't inter operate, and why should they? Microsoft wrote OOXML for itself, not for others.
It is my opinion that Microsoft peculiarities in OOXML, together with the fact the specification is over 6000 pages long, would greatly hinder the ability of other parties to develop products that would completely, or near completely, read and manipulate documents in that format and to the extent that it would render it practically difficult to work with as a universal standard.