Use a little bit from multiple sources. I've used Google Docs, but overall it's only a miniscule portion (maybe 1% or less). LibreOffice shows up, but again only as a very small share (maybe 5%). The rest is divided evenly between Office 2010 (used at work) and Office 2013 (used at home).
Of the different options, I vastly prefer the 2 versions of Office. I suppose, however, that's because I've been using Office products for a very long time -- Word & Excel (v. 6.0 & 5.0, respectively) were the first Windows-based word processor & spreadsheet programs that I learned, & I found it extremely easy to move to them from the DOS-based WordPerfect & Lotus-1-2-3 that I'd used before that. Sure, the introduction of the "Office Ribbon" was maybe a minor hiccup along the road...but I'm the kind of user that not only still remembers a lot of the old keyboard shortcuts for Office & Windows, but still uses them because it's faster for me than clicking through the menus with a mouse.