The general gives an interesting interview to Foreign Policy:
While general concepts that proved important in Iraq may be applicable in Afghanistan—concepts such as the importance of securing and serving the population and the necessity of living among the people to secure them—the application of those ‘big ideas’ has to be adapted to Afghanistan. The ‘operationalization’ will inevitably be different, as Afghanistan has a very different history and very different ‘muscle memory’ in terms of central governance (or lack thereof). It also lacks the natural resources that Iraq has and is more rural. It has very different (and quite extreme) terrain and weather. And it has a smaller amount of educated human capital, due to higher rates of illiteracy, as well as substantial unemployment, an economy whose biggest cash export is illegal, and significant challenges of corruption. Finally, it lacks sufficient levels of basic services like electricity, drinking water, and education—though there has been progress in a number of these areas and many others since 2001.
To analogize this in terms on peoples' minds right now: In relative terms, we did Iraq in a climate-controlled indoor stadium on Astroturf. By comparison Afghanistan will be fought out on a muddy field in a relentless downpour with no stadium lights and refs who don't understand the rules. Should be fun.
P.S. Remember when McCain misspelled Petraeus? Ah, memories.