I believe this question would fit better in the Rules Forum, and I believe it was already mentioned there, but anyway:
You can use it against anyone who sees you (every observer), and anyone who fails it loses his Dex Modifier to AC if you attack him.
This means you can feint against more then one target (though you can only attack one of them), AND you may attack in the same round, not one round later.
So, if you are good at bluffing, this gives you a guranteed sneak attack every round without tumbling in flaking positions, becoming invisible or surprise the attacker due to high Initiative.
And since everybody looks somewhere else during your next action, you might still have oppertunities to do something else. I wonder what would happen if you, as an example, tried to cast a spell (not to likely for a rogue, but perhaps bards), if you would be subject to AOOs and so on.
And perhaps there are some other nice tricks (hiding something, including yourself?).
Mustrum Ridcully