I own Microsoft Office 2010, but I have to say I am quite impressed with Libre Office. It feels much faster and snappier.
I use Kingsoft Office free because I find it can open some Office Documents better than Open Office or Libre Office.
Microsoft Office. I've tried other options but i always come back to Microsoft Office, i'll just stick with it from now on. No need for anything else.
Microsoft Office - for everything that matters LibreOffice (PortableApps.com version) - just to accompany its development Google Docs - for fast online viewing of files inside Opera with the help of gPDF
Microsoft Office - used by 98% of computers worldwide - Office has no alternatives and all free versions I have tried had compatibility problems opening documents originally created by MSO. At home I use Office 2007 I bought back in 2006 - at work I use Office 2010/2013 and I am thinking of upgrading to 2013/365 at home as well.
LibreOffice for me, both on Windows and Linux. I would not pay a single cent for any version of MS Office, as long as there are better AND free alternatives.
Ditto Wendi. While I don't believe there is a true substitute for Microsoft Office (and specifically Outlook), the enhancements in MSO 2013 simply don't interest me.
LibreOffice, Seeing Word Perfect on the list bring back a few memories. I had not realized it was still around. I really like Word Perfect, it was painful to switch over to Microsoft Office when my company did. Probably why I dislike MS Office so much.
Office 2010 at home and at work, with custom security-oriented Group Policy settings enforced courtesy of Microsoft Security Compliance Manager (a nice freebie for those inclined to tweak things to the nth degree).