You have to understand how deeply N Kor hates the US. At the end of the Korean War we had pretty much laid waste to everything they possessed including the infrastructure of the country. Fifty years later they still intend to make us hurt! Couple the intense hatred with the insanity of the national leadership stir in a nuclear bomb or two, and you have the fixins for an attack on the US that could make 9-11 look pretty small. Would they do it? You bet!
I'd like to think that as much as a relatively sane person can, I do.
S. Korea and Japan are more willing to avoid conflict than we are because of their recent history - but I will say this, nobody I know would predict what N. Korea will do, is doing, or thinking.
Maybe Churchill would say, "It is a riddle wrapped in mystery inside an enigma; but perhaps there is a key." But then he was talking about Russia, and the key was their own national interest. With nK, if it's not national interest, it is more probably what's in Kim Jong Il's best interest.
Without knowing how sane he is, or hateful of us, it's tough to guess how far he'll push this. But it is a fragile country right now, and it's not in his interest to push this farther than simple concessions.