In regards to the use of torture as described in 1984, its most striking feature is that it is not used in the classic sense to extract a simple confession or give up information (usually followed by the elimination of the victim), but rather to convert Winston and Julia to the party's thinking and make them compliant citizens in Oceania. As O'Brien says in the second chapter of part three "You are a flaw in the pattern, Winston. You are a stain that must be wiped out....We do not destroy the heretic....we bring him over to our side, not in appearance, but genuinely, heart and soul."
Whilst Winston is at first subjected to the usual bodily beatings one would expect with torture (causing him to plead for them to stop), it is later with a combination of the physical and psychological torture under O'Brien that Winston really begins to break down. He slowly comes around to the party's twisted sense of logic, as demonstrated by his acceptance of completely illogical math equations.
The importance of Room 101 cannot be understated for its effect on victims. A good part of its effectiveness comes from the unknown. Before the victims are taken there they are already in a high state of terror as a result of the room's sinister reputatation, but at the same time are unsure of what to expect. In Winston's case he is confronted with one of his most personal, deep seated fears - having rats attack him whilst in a defenceless state.
Whilst both Winston and Julia do recover physically from their ordeal, it is in their radically altered psychological state that we see the ultimate triumph of the party's torture. As Juia states in book three chapter six "And perhaps you might pretend, afterwards, that it was only a trick and that you just said it to make them stop and didn't really mean it. But that isn't true. At the time when it happens you do mean it." They have become reduced to hollowed out shells. Not only has their betrayal of each other under torture reduced their love to a completely meaningless state, but they have lost all sense of individuality and become loyal converts to the collective state.