Eh, as a level 60 warlock we are pretty gimped in pvp. I agree in duels, we are pretty damn good, but that is because we can prepare for the battle and have the right pet out for the particular class we are fighting. In a normal situation we aren't that lucky.
For example a rogue is going to own us every time unless he is absolute shit. The only chance we have is if we have free action potions on us. If not we spend the first 3/4 of the fight stunned, and by the time we get out of that it is over. We only have two defensive spells, they share the same diminishing returns timer, one requires us to have a specific pet out, neither are instant cast, and everyone in the game can break them due to pvp trinkets/will of the forsaken/blacksmithing trinkets.
The only other strategy we have is to go demonology specced to get soul link (I'm not demonology at this time, but affliction). Unfortunately, that gimps our best pve abilities and without dark pact we lose a lot of our man efficiency. Also, all of the demonolgy talents are shit ,with the exception of demonic embrace and soul link. While soul link will allow us to survive longer in one on one pvp, it is pretty worthless in group pvp. Horde priests and shamans can dispell it leaving you in a bad situation.
Now don't get me wrong, I don't hate my class like some of the other warlocks in this thread, but to pretend we don't have problems in pvp is insane.