The Nokia Lumia 900 for AT&T is now receiving the Windows Phone Tango update. The update will offer Windows Phone build 8779 and have the firmware version 12223. The update will bring some of the latest features including the ability to silence the device by flipping it.The update will also improve the performance of the start up along with a “more reliable boot sequence following full depletion of the battery”. Lumia 900 users will also have quicker access to their camera, allowing them to get to it with a quick press of the dedicated camera button.
The most visible item that this update delivers is one of the newest features of the Windows Phone platform: the intuitive “flip-to-silence” function when receiving an incoming call.Once you receive the update notification, you can receive the update by connecting your device to your computer using the Zune software for Windows or the Windows Phone connector for Mac.
There are also enhancements to the performance of the startup sequence - most notably providing a more reliable boot sequence following a full depletion of the battery – as well as enhancements to camera performance when utilizing the popular “pocket-to-photo” feature that allows users to open the camera application on a locked device with a simple press of the dedicated shutter button."-Nokia
source – WPCentral