Since the upgrade from 11.10 to 12.04 the battery icon / power indicator is not shown any more in the menu bar.
I went to 'system settings'-->'power' and tried to set 'show battery status in menu bar' to 'always', however the selection button seems to be corrupt. Strangely, when I open the power settings dialog, the 'show battery status in menu bar' field is set to an empty string instead of showing one of the three possible choices. When I click on the small arrow next to it, the three possible choices are shown. Whatever I select, upon closing the settings dialog and reopening it, the selection field is back to empty.