OASIS Open Document Standard
I have been using OpenOffice.org 2.0 beta this week (wrote an article for DevX on Ruby) and it is spectacularly good. I own a Word 2000 license, but I don't even have it installed. I did use Word for two recent books - but only to save out files created by OpenOffice.org for sending to my publishers. OpenOffice.org uses the new OASIS Open Document Standard. Perhaps comparing Word 2000 to a 2005 version of OpenOffice.org is not so fair, but so it goes...
Open Document standards are such a good thing for so many reasons. The world would literally be a better place without proprietary document formats (especially Microsoft's because they seem to go out of their way to make their document formats incompatible and difficult to work with).
I think that one "killer application" of open document formats will be web based content management systems. Last year I designed and wrote a web based CMS system and dealing with Microsoft Document formats was a pain until my customer licensed dtSearch which handles a variety of document formats. For "rolling your own" support for handling a variety of document formats, see my DevX article last month on Lucene that included support for indexing and searching Microsoft, OpenOffice.org, AbiWord, etc. I also have support for this in my KBtextmaster open source project.