Abiword has a few really neat features, including real-time collaboration over XMMP (Jabber), meaning you can use your GTalk account (or any other Jabber account) to collaborate with a friend. This is really powerful. It also includes basic OOXML support. Abiword doesn't handle complex styles well, so a lot of advanced style information was lost, but the basic format of the documents survived nicely.
The release notes:
Add the following to your software sources to get Abiword 2.6 and try it out.
deb http://ppa.launchpad.net/abiryan/ubuntu hardy main
deb-src http://ppa.launchpad.net/abiryan/ubuntu hardy main