Matt thinks Brzezinski's endorsement of Obama is significant in that it shows an alternative foreign policy consensus beginning to emerge. Will it help win Obama votes in the early states? Not likely. Still, it's certainly relevant to wonder how Obama and Clinton might approach foreign policy decisions differently and Brzezinski seems to think Obama will be less conventional.
Still, on the only question that matters politically at this point: what to do about Iraq - Clinton and Obama have been sounding very much the same.