Is Demonology Warlock viable spec on MoP ?

Hello guys, I've never played MoP and I will start playing it with friends on Frostwolf realm.

I was thinking to make a warlock, but only if the Demonology spec is good.

So to the question. Is Demonology Warlock viable spec?
Are they in demand for raids and PvE?
Are they good in PvP?

in MoP demon lock is fairly good for pvp and that kind of playing style but normaly a group wants a destro lock for chaos bolt i could be rong tho idk if locks work on this server but i have alot of exp with locks