The complicity of the ISI in the Afghan insurgency is evident if one considers the policy of arresting Taliban commanders who are deviating from the agenda of a jihad against the western troops in Afghanistan. One of the most striking examples was the detention of Mullah Beradar last year. Beradar was the number two of the Taliban (although one could say he was rather number one because Mullah Omar has has not been seen nor heard of for a long time...). Beradar was ready for peace talks with the Afghan government. After he had moved between Pakistan and Afghanistan freely the Pakistanis suddenly arrested him, but kept him away from the Americans. I think this arrest should send a strong signal to any of commanders who was thinking about a policy change towards Kabul.
Although I don not have a proof, I personally think that the Pakistanis sold bin Land to the Americans because he was of no value to them any longer. I see his death more as a symbolic success rather than a real tournaround in the struggle against terrorism.