About the transition:
Right now it's too early to tell whether the transition will be smooth or rough.
From about 2009, there was an internal power struggle in North Korea that many detected. Many power players were assassinated or died under mysterious circumstances.
One of the most leading factions in the power struggle is Kim-Jong-Il's brother-in-law, Chang-Sung-Taek. He is reputed to have been the second most powerful man in North Korea (after Kim-Jong-Il himself), and is holding several powerful positions.
Another faction is lead by Oh-Keok-Ryul, a general who was formerly the number second in North Korea, but had recently fallen out of favor by Kim-Jong-Il in favor of Chang-Sung-Taek. He still remains very powerful, still commanding respect in the North Korean military.
There are of course, many competing interests and characters, and a power struggle, even a minor one, seems likely to happen.
There's one thing that some people don't seems to grasp. It's that Kim-Jong-Uen's succession will/is very different from Kim-Jong-Il's smooth one. Kim-Jong Il was prepared for many years to succeed Kim-Il-Sung, and held military command and such important positions for many years before his father's death. He also probably engineered the 1983 Yangon bombing in Burma which almost killed the Korean president Bak-Chung-Hee, and the Korean Air Flight 858 bombing, which killed all 115 people in the airplane.
However, Kim-Jong-Uen only had less than a decade to prepare, and the rapid weakening of Kim-Jong-Il's health sped it up. He's very young, much younger and inexperienced than Kim-Jong-Il was when he succeeded, and although appears to be very smart, is still yet very much young and inexperienced.
It will be a very rough transition. I wouldn't be surprised if many key people in North Korea are killed or likewise eliminated