So my girlfriend managed to pick up a yellow 920 at a Microsoft kiosk after her AT&T order has been sitting in processing forever.
She was complaining of really bad battery life and was planning to return the phone and just wait for AT&T.

She told me to try the iheartradio app so I did. The next day I noticed that my usual battery life got a lot worse. I put 2 and 2 together and uninstalled the app and battery is back to normal. I told her to do the same and she's getting amazing battery life now.

So just a heads up, this app kills battery life. At least it did for us.