I was never a fan of the whole Western participation in the Afghan civil war. My expectation was a combination of raiding and bombing as response to 9/11, and was pleasantly surprised when a regime change was effected in Afghanistan without much effort.
Everything that happened later (the whole occupation & nation building stuff) never convinced me at all. The West should have left Afghanistan - and left it to the Afghans (Uzbeks and Tajiks, actually) in 2002.
The discussion about a new Afghan strategy (and withdrawals) is raging in many Western countries now, and most arguments in use old and well-known.
George Will's explicit pointing at the Bosnia experience in nation building is a nice exception. I didn't look that closely at Bosnia as an example and parallel yet.
Western troops have been in Bosnia and Herzegovina since late '95. About fourteen years of nation-building (mostly in peacetime) were not successful in creating a stable state or nation. The ratio between population and Western troops was much better and the culture is much more 'Western', literacy much higher and religious/ideological issues much less relevant than in Afghanistan.
In short: We had a test run for ISAF in SFOR, and the test run is not even close to the ISAF expectations despite much more favourable conditions.
Some recent discussions were about the option of re-focusing on the real enemy AQ and get rid of the Taleban obsession (Biden, Krulak and many others). Maybe that's a good plan.