Okay, so, I originally was a deep Demonology spec, which I really enjoyed, but that build wasnt putting out the DPS that I was looking for in raiding. I switched to the standard 0/41/30 Demon/Destruction spec for raiding. This build gives the Warlock a felguard but also gives more damage and crit in their destruction spells. I have more fun with this spec than my original spec, while being more useful in raids (well, as useful as warlocks can be in raids).
After dual spec came out, I debated with a deep affliction and a deep destruction spec for my secondary. I eventually went with a deep affliction spec. Affliction doesnt seem to put out the DPS that it once did since two DoTs no longer stack, but it does allow for a little more self healing ability. One thing it does put out is huge threat generation, which I sadly found out many times in the Hodir fight.