I've had a warlock main since the end of 2007. I also played him wrong until level 70 and then still probably played him wrong but then either didn't care, or by the time we started raiding in Wrath, I could dps enough it didn't matter. I've basically been playing him as Destruction the entire time. I tried Affliction for a month I think and still have it as my secondary spec, but I never use it. I tried Demo for PVP, but found out I've gotten so use to Shadowfury that I couldn't spec deep enough into Demo to be really a Demolock. So Destro all the way...and burn them all in fire (not green fire mind you. Never did find that quest).
Chaos Bolt is still one of the most fun additions to Warlock. A massive nuke that always crits. And by level 99 I had Improved Chaos Bolt which reduces the cast time by I think 2 seconds. So with full Embers I can almost spam Chaos Bolt as fast as Incinerate. I don't remember what the damage is now, but at 90 in epic raid gear (pre-squish) I've seen locks with 2 million damage chaos bolts. I managed 1 million. Last one I think I saw was 80,000 damage at level 98.