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Want maximum MS Office compatibility? Get MS Office.
Want free? Get LibreOffice/OpenOffice.
Want easy to use office apps that simply make sense? Get iWork.

I'm a fan of iWork. I find that it generally is quite compatible with MS Office documents but is much better to use than MS Office.
 
For documents that are primarily printed, or for my internal use, or to share only once or twice with others - iWork.

For documents I will need to send back and forth several times to others - NeoOffice.
 
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