Really big fan of the simplified permissions feature. It's something I've always wanted that Android never had. In addition to the supposed battery usage improvements, I'm looking forward to the new streamlined Android Pay features.
"The M Developer Preview introduces a new app permissions model which streamlines the process for users to install and upgrade apps. If an app running on the M Preview supports the new permissions model, the user does not have to grant any permissions when they install or upgrade the app. Instead, the app requests permissions as it needs them, and the system shows a dialog to the user asking for the permission.
If an app supports the new permissions model, it can still be installed and run on devices running older versions of Android, using the old permissions model on those devices."
https://developer.android.com/preview/features/runtime-permi...