I've had a Warlock since Vanilla, even got the Dreadsteed at lvl 60, but it wasn't until MoP that I played one seriously, and I LOVED it!!! It finally felt like something more than just "a Mage with a pet".
With the KJC nerf, though, he class is right back to being that "Mage with a pet" except even Mages can have a pet.
Frankly, I think Blizzard took the laziest route possible to "balancing" KJC. How about instead of completely gutting what made it so fun, you have it reduce your movement speed, damage, or even spell-range? Something that keeps the same "feeling" of playing a KJC Warlock, without being quite so powerful against other classes)
As it stands, though, I just find the WoD Warlock to be boring as shit, which is a shame since my Betrayer set will be left to rot on a lvl 90 toon.