With Moutain Lion, Apple has greatly simplified the battery indicator in the menu bar. Before, you were able to configure it to show the (battery percentage) or the (remaining time) to the right of the indicator graphic, or to have neither. Now, the default representation is to only show the indicator graphic. Clicking the indicator pops up a menu that displays the remaining time, and that presents you with a Show percentage checkbox. If checked, it will display the battery percentage to the left of the indicator icon, without round brackets.
The battery indicator in OS X now works almost exactly the same as in iOS — although its look still differs between both operating systems; iOS even has different representations of the battery indicator depending on the look of the statusbar.
This is another one of those changes meant to unify the OS X and iOS experiences. Those of you that preferred to have the remaining battery time always be visible in the menu bar will likely be disappointed by this particular change.