Joyner is basically where I am:
My takeaway from all this was that President Obama had come to believe, as had I, that the very ambitious set of goals articulated by his predecessor were unattainable but that he believed saying that was politically untenable. Since he had campaigned on Afghanistan as a "war of necessity" that the Bush administration had under-resourced to pursue a "war of choice" in Iraq, he couldn't very well say, mere months into his term, that Afghanistan wasn't worth it after all. Further, bugging out before the job was done would lead to charges of weakness that no president, particularly a Democratic president with no military bona fides, wants to fight...
[The McChrystal controversy does] provide yet another opportunity for the president to decide what it is he wants to accomplish in Afghanistan and what resources he's willing to put into it. The two should mesh. Further, the critics are right: Whatever the ultimate plan, the key players have to be on the same sheet of music. So pick people committed to the president's agenda, whatever that may be.