Now users are advised not to install Windows 10 a la default but be aware and pay ample attention to risky privacy settings.
Go to Privacy Settings via Start > Settings > Privacy to change the default settings, please.Standard all txt and spoken txt goes directly to Redmond so the personal assistent MicrosoftContana could know to learn you better.
Also the content of your address list is uploaded to MS. Every visited webpage will be known to MS to be checked by SmartScreen Technology.
Windows 10 will let you share your Wifi passwords with friends from social networks.
Every program and app can read out your personal ad-ID.
The new browser Edge is going to show you personalized ads.
All your location history is continuously saved by the PC. The apps you will install will directly recognize who you are /name-picture.
So why there is no-one here in this thread who has questioned why Windows 10 is handed out completely free? MS certainly wants you and your new OS to be the MS and Bing product.
Not convinced yet, then read here:
http://articles.forensicfocus.com/2015/07/27/project-spartan-forensics/polonus