Word compatibility inside the Windows versions is already less than perfect. I have had great success using both OpenOffice, and now LibreOffice to edit highly technical scientific Word manuscripts- including revision tracking and comments, and dealing with asian font mismatches with my American installations. MS broke their own lock on proprietary formats years ago. the argument is driven more by fear/uncertainty/doubt than actual exploration of the issues. We regularly have Windows Word users 'breaking' each other's document formatting on XP and Win7 systems. The .docx debacle has only made the problem more visible. Compatibility arguments do not long survive actual testing of meaningful differences and honest comparisons with a 'gold' (pure Word user) experience.