At the risk of getting an infraction for responding to a terrible post (my 3rd), but this is the Questions thread:
Leveling is a joke these days, especially as a warlock - so it really doesn't make much difference what spec you level with. If you're seriously interested in min/maxing leveling, your best bet is probably Affliction > Demo >>> Destro.
My preference for leveling has always been Affliction for the huge mobility, little downtime, and ability to drain-tank if needed. Use the Imp for free damage until you get to 30 for the Felhunter. Points would be something like this. After you pick up Haunt, go to Demo then Destro since you'll be in your 80's and doing more difficult dungeons for sure.