There are a lot of legitimate criticisms to make of the US intervention in Afghanistan. Some targets of legitimiate criticism are such things like use of UAVs that end up missing targets and killing innocent people, things like eschewing an offer to co-operate with the Islamic Republic of Iran on an issue (which in hindsight takes on an uglier edge than it did at the time) and to a very real extent bailing out of this war to go fight Iraq a second time. Another reality is that he's risking either war or much greater involvement of Pakistan, and if we go to war with Pakistan it magnifies every disastrous consequence of a war with Iran sixfold or more.
One area that I neither understand nor consider legitimate is to attack the current President over how he's handling things like the (complete lack of leadership on the part of) the government run by Hamid Karzai. Afghanistan's been in one or another war since Leonid Brezhnev approved the Soviet Armed Forces' invasion of it. This was a long and bloody conflict, and once the Soviets withdrew there was a civil war that the Taliban proved the most formidable faction in until we came in. Either way, this will be in December 30 years of war in Afghanistan.
Thirty years of war in Germany were sufficient to level the place and critically weaken it. Germany didn't recover for a matter of centuries. 27 years of war in what is now the People's Republic of China arguably contributed a great deal to why the PRC is what is today. Long periods of war tend to malform societies affected by them, and they tend also to encourage corruption, graft, and to weaken over time desire to participate in or to even bother with the infrastructure of society. Afghanistan's already seen the results of one superpower fighting in it, and in October the USA will have spent eight years there. And if we still have significant number of troops there in October 2011 then we will have been at war there as long as the Soviets were.
President Obama is an average leader. He's capable of more than even his supporters sometimes profess that he is, but he's also capable of seeing through at least enough of a military victory to suppress the Taliban. President Obama has inherited a crisis 30 years in the making, and IMHO, while as noted there are many legitimate criticisms of his war effort there to make, I feel that the President should be given some leg room to fight the war as he wishes, by both his supporters and his critics, to shape up what's not working and to improve what is. Because to expect an average leader to improve on a legacy that started with Premier Brezhnev is frankly to expect him to work miracles. The President is just a man, and he does make mistakes.
I suppose if I were to sum this up in a sentence or two it would be that Afghanistan's been in chaos for 30 years. President Obama as an average leader has more promise to work through the legacy of 30 years of war than his predecessors. Yet it is not fair to blame him for all the mistakes dating back to President Carter and the leadership of Leonid Brezhnev.