Well it seems that with windows 10 there will be a real revolution in terms of new features and how the operating system will be managed, it will not be an “object” to buy and use until you decide to upgrade it. The new Microsoft operating system will be seen as a service (Windows as a service or WAAS?!): “This is more than a one-time upgrade: once a Windows device is upgraded to Windows 10, we will continue to keep it current for the supported lifetime of the device – at no additional charge”.
For a full list of the changes introduced from the usage point of view there is no reason that I list them because there is the official microsoft page that presents them to you in the best way:
Personally the things that impressed me the most were: 1- the complete integration between all devices, nothing particularly innovative, you do it from a while using the various cloud services, but here we are talking of the same operating system that runs on devices of all kinds (pc, tablet and phones) so the user experience is truly seamless. 2- HoloLens… something between the google glasses and an oculus in terms of size and functionality that allows you to see real-time augmented reality. Fantastic! Will create a new world of ideas to develop.
The integration with Cortana (the Siri from Microsoft, but it seems much more powerful) is interesting even if we must see how much will be used everyday.