Three years later

By way of Xnoubis, I have Juan Cole's summary of 9/11's consequences thus far.

In order to evaluate the aftermath of September 11, we first must understand that event. What did al-Qaeda intend to achieve?
...
Bin Laden hoped the US would timidly withdraw from the Middle East. But he appears to have been aware that an aggressive US response to 9/11 was entirely possible. In that case, he had a Plan B: al-Qaeda hoped to draw the US into a debilitating guerrilla war in Afghanistan and do to the US military what they had earlier done to the Soviets. Al-Zawahiri's recent message shows that he still has faith in that strategy.

The US cleverly outfoxed al-Qaeda in Afghanistan, using air power and local Afghan allies (the Northern Alliance) to destroy the Taliban without many American boots on the ground.

Ironically, however, the Bush administration then went on to invade Iraq for no good reason, where Americans faced the kind of wearing guerrilla war they had avoided in Afghanistan.

Al-Qaeda has succeeded in several of its main goals ...

It's a very clear, and depressing, summary.