It's going to be difficult to know for sure what the final product for this class will be until probably a month after the expansion. A wave of adjustments for all classes will be in quickly. (I hope)
At this point however, I'm not sure what the viable PVP spec is going to be for locks. And even then, I think we're going to see a distinct separation, not only in PVE/PVP, but BG/Arena.
Why? The affliction tree is really very awesome, both in utility, and damage. The cons found in NO survivability will be washed out by having effective teammates in a pre-made. That's why I'm giving two thumbs up for affliction in BGs.
Arenas - Blizz really gimped Soul Link (and Fel Stamina). Despite my early excitement with this buff because of the bump to 3rd tier, I find myself wanting more. The buzz right now is full demonology. Metamorphosis? 51 point talent, lasts ONLY 45 seconds, and has a 3 minute cool-down? I feel like locks are being forced into it for Arena since there are no alternatives if you want to live longer than 15 seconds. I've had mages and ret pallies beat me down in 5-6 seconds (I have 500 resil, 13k life). The smushyness (lol) is overwhelming.
Just some food for thought,
Heden