Today Sun announced an Open Document plugin for MS Office. I like some quotes:
In other words, we’ve done what Microsoft could and should have done in the first place instead of FUD-ing and fighting. We’ve used freely available open-source code to build seamless, intuitive support for ODF into MS Word. No unmaintainable XSLT. No funky, redundant additional menu items. No tortuous workflow designed to make users treat ODF as second class. No pre-requisite for the OOXML add-in to make it work. Just peer support for the industry-standard file format, using open source rather than building from scratch so the improvements that are made to OpenOffice.org lead to improvements in the plug in.
Some screenshots here.