Woohoo, first post here, chaps! :-D
The Death Penalty, if performed efficiently, would be a very beneficial aspect to society. Even if most punishments are little effect as crime deterrents (imo, fighting the cause of crime makes more sense than dealing with a crime itself), the Death Penalty still eliminates scum from the gene pool.
The problem is the complexity. Being logical, if you're going to kill someone, why have Death Row when they're going to die anyway? Just shoot them in the head and be done with it.