A thread on Small Wars Journal's Council talks about the difficulties of applying the "Surge Strategy" to Afghanistan. There's a link to some information on Herschel Walker's blog, The Captain's Journal, but much of it is "For Official Use Only", so I'm somewhat hesitant to link there. However, I'll just say that reports from the field indicate a much more sophisticated enemy force. The problem of fighting counter-insurgency/hybrid war is also compounded by the difficulties of maintiaining a significant NATO force with ground supply lines through Pakistan increasingly dubious and a near-imminent closure of an air route from Kyrgyzstan.
On the tactical side, the rugged terrain makes much of the technological improvements that saw success in Iraq invalid. Up-armoured Humvees and the new MRAP vehicle are too heavy and cumbersome to use on the trails and mountains of the country, leaving troops to rely either on travel by foot, lightly armoured vehicles or helicopter.
I'd definitely say that NATO has its work cut out for it in the next year or so.