Ive been using OpenOffice as a free alternative to MS Office. Of course, Id been using NeoOffice prior to Apache taking over OO.
A former coworker of mine was ranting about how much she hated Word - it kept eating documents - her words - and crashing. I recommended OpenOffice to her, and shes been happy ever since. It reads/writes all the formats, has cleaner code that MSO, and has a look and feel similar enough to MSO to keep the user from having to relearn too much.
That, and the documentation is certainly better.
Im sure there will be those who disagree, but in my opinion, open source is certainly better than proprietary/commercial any day.