"n Ubuntu 12.04 Precise Pangolin alpha 2, when launching an
application, the menu is initially displayed on the top bar and is
only hidden after an amount of time which can be modified (along
with the fade duration) through CCSM.
"Until now, the menu would always be hidden and only show up on
mouse over, but this behavior made the menu hard to discover for
new users, so with this change, the Unity developers hope to make
the menu easier to find. And in case you were wondering: no, you
can't set this to a huge value to basically disable autohiding the
menu - the maximum value is 10:"