I came across a post on xda that suggested a very simple workaround for the battery drain issue the TF101 seems to have with ICS. I'm posting that here because it seems to have also cured my random reboot/shut down issues, at least for the past 24 hours.
Go to Settings, Developer Options (click OK at the warning), and find the "Stay Awake" option. It should be unchecked. Check the box. Wait a few seconds, and uncheck the box. Back out to the home screen.
The theory is that this option is in a pseudo on-off state and this is preventing the TF101 from falling into a deep sleep. Checking/unchecking the option actually turns the option off, stopping the battery drain. It worked instantly for me and also stopped my rebooting issues. Granted it's only been 24 hours for me but so far, so good. Link to the xda thread is
here.
My apologies if this was already posted.