A Newsweek article from two weeks ago painted a picture of Afghanistan that was perfectly stable until the Soviet invasion, but this is completely false. It was Afghanistan's instability and successive coups which prompted the Soviets to invade in the first place. The most oft-quoted period of stability occurred from the early 1930s to the early 1970s, when a number of reforms led to a democratic state, which even gave women the right to vote. Nevertheless, it was mired by corruption and economic strife (sound familiar), and ended in a coup in 1973.
If we are going to set up a government in Afghanistan, let's not pretend it will be a perfect democracy. This is not what they want, nor what they will recognize. It should simply be able to deliver justice, police its own people, provide security, and be able to provide basic services (water, food, schools, electricity). It may not even be a democracy as we know it at all. This is perhaps the best "success" we can hope for in Afghanistan.