Sorry for pushing up an old topic (Well, actually only 3 days old) but I felt that I wanted to add some realistic views on the Korean unification...
As I had posted earlier, I don't know if all South Koreans are really eager to reunite with the North in a rapid fashion. Looking at history, they can see what kind of problems it could trigger just by taking a look at Germany. The discrepancies between the two Koreas in nearly every category (economy, society, political system) is certainly wider than the two Germanies at that time.
What makes things even worse is that Kim's regime is probably determined to hang on to power. A unification scenario would make overhauling the regime very likely, so instead of unification of would be the South absorbing the North (Like in Germany). This scenario is probably not that desirable from the perspective of North Korea's regime at this time.
Im my opinion, North Korean security policy is pretty much regime survival. One crucial factor is that the most powerful state in this mess (USA) doesn't grant it full sovereignty and the rhetoric used by that asshole Bush has definitely added fuel to the fire.
After the shift in the balance of power in the beginning of the 90s (Soviet Union declined in status in the region) North Korea found itself without the support that it used to have, making the isolated form of society increasingly difficult to maintain, especially when faced with severe humanitarian crisis. (famine in 1995 e.g.) and one mean to extort some form of recognition, ANY form of recognition by the international community and much needed aid was the threat of a nuclear arsenal, which Pyongnang decided to employ.
Even though regime collapse seemed to be what many are hoping for, it is unlikely to happen in a short amount of time. Or, to put it differently; all the outside powers involved (South Korea, USA, China, Japan) should employ a strategy which solidifies the status quo and prevents any drastic alteration, because any event which is perceived by Pyongnang as regime threatening could lead to military escalation. Even though the US and China are not directly pitted against each other in a fashion like the Taiwan strait, military intervention in Korea could lead US troops pretty close to the border of China, something Beijing wouldn't be amused about.
Some time ago (Last December I think) there were secret talks between North Korea and the US. Even though North Korea broke off the 6 party talks about its possible/probable nukes, possibilities for negotiations are still there and kept alive. It seems that the US is/was willing to conduct talks with Pyongnang, even hinting at the possibility of offering some form of normalization of diplomatic relations, emphasizing that the US doesn't want to take any military action against North Korea. Bush may have ruined it all with his "Axis of Evil" insanity, but I believe hope is still there.
My view is that there many problems to consider in unification, not just "US is stopping Korea from uniting" and that they have to be solved before anything else can be done.
I just hope to god that the US and China won't get in a spat over Korea or Taiwan... of course the big losers in those scenario would be the innocent people that happen to live in those areas... like my family... -_-