Nokia today said that it is pushing a minor system update to the Lumia 900, which is sold by AT&T. The update fixes several bugs, smoothes out the start-up sequence, and adds the "flip-to-silence" feature. The update also makes improvements the camera's behavior. The update must be installed through the desktop Zune client or Windows Phone Connector for Mac. It is available starting today.
This is an Android feature offered in HTC phones since 2.2. I have this on my MyTouch4G (T-Mobile). Pick it up and the ringer will silence, flip it over the ringer will silence. If you are on a call, just bring the phone away from your face, and put it face down on something and it will turn on the speakerphone as well. Its a novel feature, that ironically, I found MOST convenient and the "move to silence" feature something ALL PHONES, even non-smartphones should have. I cant stand peoples blaring phones in public who are too stupid to silence the ringer - they keep looking at their phone "Should I answer?"