*Fizzle* *Plop*! Into the ocean like last time?
Actually their shorter range stuff, their Scud knock-offs and the Rodong/Nodong series of MRBMs are not bad. Not something I'd want protecting my Country, but not something I'd appreciate threatening my Country either. All of South Korea and a pretty good swath of Japan are within a Rodong/Nodong's range while carrying a 1000 Kg payload.
That 2200 lbs or so is enough for a big bang, a serious chemical attack, or probably enough for a first gen nuclear warhead and RV. Given it's 1 or 2 Km CEP it isn't accurate enough to take out specific military targets (without a nuc as a warhead), but no-doubt works just fine as a terror weapon.
I think the other poster is right. They are seeing the sweet deal Iran wrangled and they want in on that. They'll make a lot of noise here and see if they can get Kerry to "negotiate" with them. :-/
If I were Japan, I might consider making some noise of my own. Park one of their SM-3 equipped ABM cruisers (I think all 4 of their Kongo class have been converted/upgraded?) near NK's declared safety zone. If they fire out to sea, as soon as that thing crosses out of NK coastal waters...shoot it down. Demonstrate just how well ABM works. Not only would it be fun and a good test. But also to show NK "we don't have to negotiate with you, you are not as big of a threat as you think you are."