Parvateshwar: So he died of Pancreatic Cancer, same thing Jobs had for those who don't know anything about cancer, which sucks, but I can't say I'm sad to see him pass on. Not sure what's going to happen with the DPRK but the military administration was strong and I'm sure they'll figure something out until a replacement figure can be found. His son is still young but perhaps he'll grow up quickly to fill the void.
Lone3wolf: Really? Everywhere I can see are reporting him dead from a heart-attack.
He had many health problems and may also have had cancer. But in the absence of any other credible reports, you are at least as right as anybody else: a heart attack got him.
I suspect that Kim Jong-Il was largely a figurehead, and that his son may be entirely a figurehead. His son certainly has no visible competence in anything. If there's actually a civilian in charge, it may be Chang Sung-Taek, who is Kim Jong-Il's brother-in-law and
de facto leader during KJI's many and long illnesses.