I'm pretty sure we don't have to worry about a payload on this particular missile. They are just trying to see if they can launch a missile that will successfully separate, start its second stage, and continue on course. The biggest problem right now is...where's the booster going to land? Japan has already said it better not land there, or they'll consider it a hostile act.
The question is will anyone do anything? Obviously North Korea will have to pay. Bush will probably tell Japan not to do anything and more of Bush's supporters will leave ensuring a Democrat victory this fall. Bush hopefully will do the right thing and make North Korea pay.