This is why I'm not so optimistic about this and think they should have announced this to begin with the class entering med school this fall.
The top of the crop of un-matched MD/ACGME applicants to very competitive fields are probably on average going to be stronger than bottom of the crop of matched DO/AOA applicants. It remains to be seen how the "AOA" programs will receive those new MD applicants. I fear the "ACGME" programs have a lot of old boys who are going to take a long time to warm up to applicants from DO schools and have nothing to gain from doing it, while the "AOA" residencies in competitive fields might have far more to gain from getting the absolutely strongest applicants than from showing any loyalty to the DO path. In that case, many MD applicants who would currently end up in their "back-up" specialty will get the "AOA" residency slots and the DO applicants will have to resign to a different field.
If I were a current MS III planning to apply to something like DO Neurosurgery (no clue if that's the best example), I would be really upset -- I'd have been planning for the past 3 years only to have the competitors changed at the last minute. While there is no reason osteopathic applicants can't have amazing scores, evaluations, grades, etc., allopathic students on average have greater access to research opportunities and influential letter writers through affiliation with more/higher-powered institutions, and those are so very prized in the most competitive fields. I worry that borderline competitive DO applicants are going to get pushed out of their fields while fewer borderline competitive MD applicants will be . . . and that's not what people signed up for when they picked their schools.
As a patient, I want the best applicants in the best training programs possible and will glad to see silly philosophical distinctions get blurred. As a current student, I feel for my peers who are having the rules of this changed mid game.