The NK nuke problem is two fold:
1) The Plutonium being reprocessed
2) The Uranium enrichmment that has been underway

What the NKs admitted to last year was that they had a U enrichment program underway since the 90's.
No one is talking much about that, which makes me think it is likely the most serious problem.
The good news of that is that U-based fission bombs are mostly fairly bulky to get any real boom out of them.
The bad news is they are building this program deep under a mountain near China.

The Plutonium problem is more obvious but Plutonium bombs are more easily hidden. The focus on Plutonium bombs and on the assumption that the program in northern NK is only U is quite dangerous.

As it is, the cards left on the table show that SK is hostage right now to NK nuke threats. It would be great to have a missle defense in place, even if it was only 20% efective, but I wonder how much good it could do against short or medium range weapons going from NK to SK.
I think Bush is doing one thing predecessors should have done: stop the pay-for-reasonable behavior game.
NK is run by a guy who thinks he is making a mega-movie. He knows all the bad guy plots and is playing them to the hilt.
Bush is, imho, properly buying time while the NK economy keeps on wandering off into complete command economy collapse, probably hurried by SARS. While getting rid of Saddam cleared the field in the ME of a guy who only starting to seriously rebuild, and who was limited on formal projeciton of military force, the NK tyrant has a whole country as his hostage, and really a whole region.
The US cannot go in on a frontal assault against the NKs unless there is no other alternative.
In Iraq we stopped a bandit while he was relatively alone.
In NK we have an on going hostage crisis.
Smart or stupid, I think Bush is being properly cautious, and is playing his cards carefully in a theatre of the real.
Ed