While the results of these studies are generally positive, I think that the "long term feasability" issue could easily be addressed by not keeping the participants on induction levels of carb for the duration of the study (6+ months in many cases) and instead allowing them to progress through OWL as the Atkins plan recommends so that each participant could find the level at which they could lose and still add in foods that many reported missing (fruits and nuts for example). While Dr. Atkins did say that people could safely stay on induction for up to 6 months (and I think this study showed him to be correct), he generally encouraged people not to unless they had a large amount of weight to lose and were not becoming bored with their food choices, so why did the researches keep the subjects at such low levels of carb for so long?
In the first study above, while 20% of the participants dropped out before the 6 months was up, that means that 80% of the participants were able to complete 6 months at induction levels of carb. I don't know about the rest of you, but I find that pretty impressive. Had they allowed the participants to move into the OWL phase, I'd be willing to bet that quite a higher percentage would have completed the 6 months.