Have experimented with dropping the mirror as a method of saving battery while shooting with ML (since the LCD turns off). It works a few times at first, but will eventually lock the camera up (the lcd goes dead, and none of the buttons work). Reboot doesn't help - get "err" code on the camera's top lcd. Before ML, I would just plug in a mini plug into the AV jack to override the lcd and save batteries without having to power the camera down. That obviously won't work with ML since the AV jack is now a headphone jack. Once camera locks up removing the battery/interrupting the power supply (if using the AC adapter) resets everything and shooting is then resumed.
Issue #125 on hold