The dual-curve display of the Galaxy S6 edge didn't really do much aside from looking really pretty when the handset first came out, Samsung repeated the same mistake that it made with the Galaxy Note Edge, which also had a beautiful curved edge display that didn't serve any real purpose. The company did add more functionality to it with subsequent software updates and Marshmallow for the Galaxy S6 edge brings the most significant improvement yet for Edge panels on this handset.
A video overview of Android 6.0.1 Marshmallow beta running on the Galaxy S6 edge shows that the Edge panels feature is much more useful than before. Aside from People and Apps Edge, there's a panel for My places which lists the most recently used apps, a Task edge panel which has shortcuts to relevant apps, a Quick tools panel which mentions the location and also contains a compass as well as separate tiles for S Planner, Weather, Twitter Trends, Yahoo Finance and Sports. All of this would really make the curved display of the Galaxy S6 edge much more useful, however users will have to wait for Marshmallow to arrive before they can take advantage of all this on their handset.
