Henry said:
Say goodbye to that horde of kobolds... 
Hmmmm.
Sleep spell can still be a somewhat potent spell, even at higher level when Empowered.
Granted, you will not affect many opponents, but HHEE Sleep is a 3rd level equivalent which on average affects a single 9th level opponent. A high Charisma Sorcerer could easily take out a low Will save combatant type with this. Granted, a Hold Person can often do the same thing even better, but a Sorcerer might not have both spells and Sleep affects monsters whereas Hold Person does not.
EEE Sleep on average affects a single 11th level opponent, but could affect as high as a 20th level opponent.
A Maximized Empowered Sleep can be used to ensure that you get a reasonable number of hit dice, even if you roll bad (9 19%, 10 44%, 11 31% 12 6%). Considering that a 12th level Sorcerer can cast this, it is not unreasonable for him to encounter 9th to 11th level opponents.
If your Sorcerer casts some version of Sleep, an opponent fails the save, and your Fighter is Hasted, the Fighter can often move in and CDG the opponent in the same round.
I think people tend to underestimate the power of the Sleep spell due to it's level cap. But, it is still a potent spell, especially in town situations where you may not want to actually kill opponents and especially when Empowered.