Just been explaining Confluence's MS Word export to someone and noticed this totally awesome feature...
We're increasingly using the wiki to collaborate on legal documents - things like version control and the ability to mark insertions and deletions, not to mention the fact that we can give access to the customer so they can review and participate, is a huge time saver.
So, I was explaining to someone how you can export a wiki page as an MS Word document, and look at what happened - it shows the insertions and deletions as tracked changes as seen above! 
Unfortunately some products don't display tracking so well (eg. "Pages" on OS X), but for word processors that do support change tracking (MS Word, OpenOffice Writer, etc), it's a fantastic bonus!
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Small correction:
I've not tried Word on the Mac.