North Korea is a threat because they have made it clear that they would like to attack the United States or our allies. However, I don't believe that we should engage in a preemptive war. It's important to watch the country and be prepared in case they do decide to launch an attack.
I believe North Korea is a threat. I realize many jokes are made about their ruler and technology, but honestly it's always the irrational persons that should be feared. We honestly can't say that we know for sure what exactly they are capable of. We know they have missiles, and the weapons they do have can hinder us greatly.
A desperate enemy or a trapped animal that posses the power to do damage will invariably lash out. Military planners in North Korea are well aware of the recalcitrance of Western politicians to engage in first strike or even aggressive defensive measures, enabling them to leverage their limited arsenal into a significant threat.
No, the threat of North Korea is not as substantial as other world powers who hold larger atomic resources. There seems to be some incompetence in North Korea's military if their missile projects are failing repeatedly. This could lead to many factors that will deteriorate the nation's influences - one would be that other countries who would have sought an allegiance with North Korea are more hesitant now that their military failures are evident.