In summary
Windows 10 was made generally available on 29 July 2015, introducing the concept of Windows-as-a-Service, a digital assistant called Cortana, a Universal Windows Platform for developers, Continuum to enable "a Windows Phone to become like a PC", and not forgetting the revival of the Start menu.
* Windows-as-a-service is meaningless unless it means one day you'll pay for annual updates. Not good.
*Cortana. pointless me-tooing
*A failure to develop and promote WinPhones meant that all the integration efforts left over from the dire Win 8 are pointless
*A replaced Start menu that's inferior to the Win 7 one, and is impossible to organise without a lot of tech skill, so for most users becomes a mess of icons, often filed under weird names that make finding them rather difficult, because you can't rename or cluster them.
etc.