http://www.zdnet.com/microsoft-goes-public-with-windows-8-1-upgrade-policies-7000016419/
Plus one I found a bit disturbing -- and you thought subliminal messages were bad, that's soooo old fashioned... now they measure your brain's reactions.
http://community.advertising.microsoft.com/msa/en/global/b/blog/archive/2013/06/05/microsoft-nielsen-partner-research-windows-8-in-app-ads-effectiveness.aspx