This is exceptionally good news.
Secretary Gates has many good qualities, but one in particular that holds promise for the future is his willingness to hold people accountable. In this he has been almost a singular figure in the Bush administration, which otherwise can only find reason to fire people when they offer honest opinions that are at variance with the official line.
This suggests that Obama, too, will be willing to value candor over toadying and competence over connections.
Gates has done an awful lot of good in his tenure so far. It's a pity that Bush stuck with Rumsfeld so long.