My quick take on the historic U.S.-North Korea summit:
we have always known no matter what the words on paper said, the actual opening and denuclearizing North Korea would be a matter of execution. The agreement still contains enough to make it a starting point, most significantly by incorporating the Panmunjom Declaration between North and South Korea that was made in the inter-Korean summit in April. Ideally, the next step would be the actual integration of the Singapore Agreement and the Panmunjom Declaration by beginning a trilateral negotiation involving US, South Korea and North Korea, to create a durable system of denuclearization and economic exchange.
I see a lot of angst about how the United States conferred "legitimacy" to North Korea through this summit. Nonsense. "Legitimacy" is not a meaningful concept: North Koreans cannot eat legitimacy, nor can they exchange legitimacy for money. Richard Nixon meeting with Mao Zedong did not make Mao any more legitimate than he was before. The meeting itself is not a reward; what matters is what happens going forward.