In the second developer preview of Android N, Google made a small change to the app switching feature. Double tapping it will still switch from app to app, but you can no longer cycle through the apps in your recents page in this way. There are also new ways to access the multi-window feature on the second developer preview. You can enable multi-window by long pressing the recents button. You can also long press the title of an app card in the recents page and slide it over to the left.