Recently the ADA issued a position statement challenging the validity of the concept of metabolic syndrome. Their statement can be found here. The ADA authors said that the syndrome lacks a precise definition, is of dubious value and its underlying pathophysiology is in question.
The AHA/NHLBI panel on the other hand said that they "found the ATP criteria for clinical diagnosis of the metabolic syndrome to be a robust and clinically useful tool." and " in the absence of compelling scientific reasons for change, the AHA and NHLBI affirm the overall utility and validity of the ATP III criteria..." The executive summary can be found here. The timing of the two publications is such that it is unlikely that the AHA could have prepared a rebuttal to the ADA paper as they were published within several weeks of each other
The clinical management recommended by the two groups is very similar- more so that their seemingly disparate characterizations of the constellation of findings designated as comprising the metabolic syndrome. Everyone seems to agree that you should treat the various risk factors per se and that there is no specific treatment for metabolic syndrome, i.e. no single pharmaceutical magic bullet to fix or mitigate the underlying pathophysiology if there is one. ADA's statement indicates they are much more skeptical that there is a unifying pathophysiology than is AHA.