The problem with sleeping and hibernation of a Macbook or Macbook Pro is that you basically get one of the other. Sleeping is good but if you’re almost out of battery life, then it’s really not feasible and you might lose your work.
On the other hand, hibernation saves your battery but recovery is terrible since it has to take everything it saved to disk and load it back into RAM. Joy above pleasurable joy.
So what the preference pane SmartSleep does is it actually has settings where you can set a default time so that if there is X amount of battery time left or percentage wise, then it will switch between sleeping and hibernation. This way, you’re never left without the most optimal solution and thus keeping your battery going for as long as possible before needing a charge. Not a bad thing to have around, eh?