Windows 10 actually looks amazing. Single core OS across PC, tablet, mini tablet, phone and Xbox One.
As a developer you can write your application once, and then deploy it to whatever devices your customer has running the Windows 10 platform, and it will scale/operate appropriately depending on whether you're sat at a desk with a keyboard and mouse, or on the train using your finger or a stylus, or on the couch in front of the telly.
As a consumer, you can buy an application once, then use it on all your Windows 10 hardware, and everything will be synced up. So you can start something on one device, then pick up another and carry on where you left off. This includes the ability to play your Xbox One games at full resolution and framerate via local network streaming using your Surface Pro tablet as a screen, for example.