While McChrystal's troop request sounds rather large, it is not enough to properly secure or occupy Afghanistan. I believe the proposed Afghan Army is supposed to have about 400,000 men, which would compare to Shinseki's proposal for American forces going into the Iraq War. This would be about right if we were really interested in securing and occupying Afghanistan.
However, as long as we are in Afghanistan, I want to see enough troops there for force protection! I also want to see them on the high ground and not stuck in some valley or canyon taking fire. I think the eight soldiers killed in the last incident were from the 4th Division, which happened to be the last outfit I served with at Ft. Lewis, Washington. I have no band-of-brothers relationship with them, having left the service before they went to Vietnam, but I do not want their lives wasted or misused.
What we did in Afghanistan was help create what became, in part, the Taliban to fight Soviet forces in that country. After that conflict, we left a civil war behind us between the Northern Alliance and the Taliban. India was one of the backers of the Northern Alliance, which Pakistan could view as a threat. It is not surprising that they supported the Taliban. Part of the anger the people of Pakistan feel toward the US is the fact that we left them alone to face this mess alone. They are now fighting the Pakistani Taliban on their side of the border. Are we going to leave them alone again? I am not very concerned about terrorists getting a nuclear weapon, but I am concerned about a possible conflict between two nuclear powers! There are no simplistic answers to these related conflicts!
My chief worry is that our leaders don't have the brains to deal with the situation.