Michael Scheuer was the head of the unit tracking Osama bin Laden. While he has not been the most reliable source regarding Afghanistan, he posits an interesting point of view in Foreign Policy.
Partly he writes:
[Obama] must act quickly on the advice of McChrystal and the U.S. intelligence community to save a marooned U.S. Army, or dither behind the harebrained split-al-Qaeda-from-the-Taliban strategizing and let more overmatched U.S. soldiers and Marines die amid the ego-building praise of effete Americans, pacifist NGOs, and the Nobelistas.
One thing that the United States and the international community must remember is that the Taliban does not just attack in Afghanistan. They have caused hundreds of deaths in Pakistan and has threatened India. The Taliban will not rest before they have hegemony over at least the Pashtun parts of Afghanistan. Still, they would rather rule all of Afghanistan and Pashtun portions of Pakistan.