now only the die hard fans that still use MS Office
MS Office doesn't have "fans". It has users who understand that it is the industry standard office software package and the importance of being compatible with other users.
No professional would ever take a chance with sharing a spreadsheet or word document and not have it open properly on a clients machine. I have personally had this happen when I was sent a spreadsheet that contained a chart created in iWork and saved in supposed "Excel Format"... It amateurish and not worth the embarrassment (not to mention the possibility of losing an account) to save $99 a year or to make some silly childish "anti-MS" statement by Apple "fans"...