I use MSO 07, and MS 10 starter on free systems. I think MSO is the best, but WPS 14 free is very impressive. The only things it lacks in the free version are autocorrect and macros. The problem is that if you buy the pro version it's not much cheaper than MS, so what's the point?
But I understand that WPS 15 is an abrupt turnaround for kingsoft. It no longer is free, but only a trial. I guess they found they were giving away the farm.
If you can do without autocorrect (which is a big deal), I would suggest WPS 14 free.
Currently, for my stuff I use Google Docs; for things that require Word or Excel, I use Office 2010 (never got 2013, rarely use Office anymore).
Tangentially related, I just switched from Evernote to OneNote (2013 is free, 2016 is free until October but I don't know if it will be after that).
The modern Win10 version of Office is decent; I may switch to that for everything.