I'm not sure why I never noticed this before, but I decided to give my LTE GNex with 2100 mAh extended battery installed a little shake and what do you know, I hear a loud rattle. So I pull the back off and realize the battery isn't fully snug. It is slightly undersized in width for the compartment -- I can wiggle the battery around in there with my finger and see some play. Not enough to affect the connection, but enough to cause the rattle. Solved with a bit of electrical tape on the battery, but wow that's disappointing. I'm hoping it's just my phone, maybe I overheated the battery one day and it warped the plastic of the housing or something.