Look, his uncle was probably as much a despicable character as any in the NK ruling party, likely performing or being complicit in any number of crimes against humanity, so no real loss to the human race here in all likelihood. What I find disturbing though is that Jong-Un has displayed callous disregard for human life in recent months in order to maintain complete control over the population.
I had high hopes for him when I learned that he'd been schooled in Switzerland, spoke English and had made positive comments in the past about the plight of the NK people. I figured he was young, idealistic, and maybe not all that different from myself -- had I been placed into a very difficult situation due to my family lineage. If placed in such a situation, I imagine that for a year or two I might have acted the part (whatever that means) in order to maintain control long enough to come up with a plan to bring some level of reforms to the country and ensure a longer-term transition to democracy.
Then again, you never really hear about a dictator who had a change of heart and became 'sane' after being able to operate with complete impunity for a while. I guess it's true when they say absolute power corrupts absolutely.
It seems that his age and boyish looks belie the fact that Jong-Il chose and groomed his successor very carefully.