One of the most important new usability features of Windows 10 Mobile is Actionable Notifications. Much like the notification centre itself, it promises to change not just how the OS looks, but how we use it on a day to day basis.
The feature lets you respond to notifications that support it from both the toast or notification centre, and lets you respond to text messages for example without leaving the context of your current app and incurring the dreaded “Resuming…” screen.
The feature is currently working in the messaging app and also in the alarm app, but it is developer dependent so will need to have apps updated to make it really useful. Microsoft has unfortunately not released the APIs yet for devs to add such support, but I suspect we will be seeing this around BUILD 2015.