One new feature in iOS is almost invisive but is meant to noticibly extend your battery life during the day. If you tend to keep your phone on your desk, when it isn't in your pocket, then if you lay it face down it will not help extend the battery. The key to this is that the OS will now use the ambient light sensor to detect that the phone is face down and if it is, then whenever a new notification comes it (message, email, etc) it will still alert you with a noice or vibration but it will not longer turn on the displan to show the message until you you actually wake the phone. This doesn't sound like much, but everytime the OS has to turn on the display, it uses a not insignificant amount of battery, so avoiding this helps save juice. The more messages and alerts you tend to get during the day, the more you will notice you battery is extended if you follow this tip (assuming you aren't always reaching over and checking on each alert).