I'm having a hard time deciding if this is just political theater, or if this is something that needs to be taken more seriously. It's hard to have a confident opinion, given the lack of reliable information out of N Korea. It's a weird situation.
Anfauglir's post hit what I'm thinking about this. A totalitarian regime require that it's subjects have limited access to information, and that they are kept in a state of fear of "the enemy"; in this case, us. So much of what occurs in politics really is theater (notice how little the US is talking about the economy and jobs lately?), and governments often have to take some sort of action to appear to be doing something. In the case of N Korea, I often wonder if the seeming bluster is just to keep the people aligned in their support, or if he's really that far over the edge.