When I returned from Iraq in 2009 I stated al Qaeda in Iraq was pretty much done as an insurgent group and would stick around only as a terrorist group. I was right.
Returning from Afghanistan I say the opposite: the Taliban is a full scale insurgency in charge of its own functioning country, the Islamic Emirate of Afghanistan. There have been many articles talking about the Taliban's shadow (alternative) government but in some large regions of Afghanistan it is the only government. In certain regions there is no Kabul-backed government (GIROA) representation at all. Nawa Disrtict, Ghazni Province has been completely abandoned. Currently, as told to me by soldiers who last ventured into Nawa over a year ago, the capitol building is waving Taliban flags and the American-built GIROA military outpost there is now an American-built Taliban military outpost. The same goes for the Korangal Valley from the documentary Restrpo which is also now Taliban controlled.
What makes the Taliban different from al Qaeda in Iraq? The primary difference is that the Taliban are native to the region and many of the commanders are locals. Unlike al Qaeda in Iraq who's main commanders were foreigners. Also, Iraq has more federalism where locals can elect their own government representatives and have some form of outlet. Everything in Afghanistan in modeled after the failed monarchies which sought to centralize everything to include having Kabul hand pick leaders on all levels.
There is no Taliban. There are Talibans
The amount of Taliban who travel from place to place to wage their jihad is actually quite small. The vast majority of Taliban are in the Afghan equivalent of their own village's national guard. They will fight in their area when needed but when not they go about their daily lives as farmers, merchants, or unemployed people. These groups have weak ties to the central core of the Taliban and often have commanders who would not care if the Taliban in the neighboring village were being killed off in a fever pitched battle. In fact, the only emotion they might feel in that situation is relief as the various Taliban village national guards have a tendency to hate each other more than GIROA or Coalition Forces. Membership in the Taliban is merely a label which fails to end tribal/regional/personal disputes. An Afghan elder to me that he supports "his" Taliban because they kept "the other" Taliban away.
Motivation also differs. A small core are die hard jihadist. A fair amount are nationalists while most are in the fight to protect their homes from GIROA/Coalition Forces/other Taliban. Unlike other winning insurgencies which everyone tries to join when they look like they are winning, a large amount of Taliban have and continue to reconcile with GIROA (even while a scary percentage of GIROA jump ship to the Taliban). As an Afghan soldier told me "everyone is just trying to survive so they do what's best to do at that moment, they do not think ahead." Motivation for these jumps show not ideological loyalty but instead short term defense of self and tribe/region.
What are the Taliban fighting for?
While Mullah Mohammad Omar and his leadership fight to return the Islamic Emirate to full power, most Taliban (I believe) are fighting for position. Everyone sees this war going on for a few more years until Pakistan and the United States decide to settle. The "pawns," i.e. GIROA and the Taliban, will then officially merge while in reality being allowed to govern what they control at the end of the fighting. Those Taliban thinking beyond the mere tactical realm realize they are fighting for position in a war they cannot win yet cannot lose.
Are there moderate Taliban?
The upper leadership of Taliban are out and out monsters. While the lower level guys may not be active monsters, they certainly are not "moderates." They are moderate in the sense that they would not throw acid in women's faces but they probably would not condemn the action either. Then again, some GIROA officials like Abdul Rashid Dostum made their name by using solar power to cook Taliban POWs alive in locked trailers..