Microsoft Multi OS booting
Microsoft patent allows the phone to only boot the necessary parts of the OS (or even Android for the occational app on that platform) on future Windows Phones!
Actually it is similar to how X-Box One have 2 OS, one for games and one for Skype/surf and so on. On X-Box One they run simultaneously though.
This can have fantastic effect on batterylife, businesses connecting to servers and so on!