After all: software companies die, but information lasts forever. If a company takes the secrets of unlocking your data to its grave, where will that leave you?*OpenOffice.org runs on multiple platforms. Currently: Windows, Linux, Solaris, FreeBSD, Mac OS X.
*OpenOffice.org is stable, and runs smoothly.
*Microsoft has made it clear that it wants proprietary document formats, and inconsistent ones at that. This may work as long as Microsoft is around and developing software that supports files created by outdated products.
*OpenOffice.org uses data formats designed to be easily interchanged (OASIS specification), and other projects are cooperating with the vision of open document interchange - e.g. Abiword, and KOffice.