Ok, specifically what?
When viewed against the context of what happened at Tora Bora, where the security cordon provided by our Afghan allies proved to be less than air tight, Scheuer's thesis that we aren't prosecuting the war in Afghanistan using the knowledge available appears to have some merit.
There's also a point made about how Pakistan traditionally has dictated, so long as it meets certain other conditions, what type of leadership shall exist in Kabul. Suffice to say Karzai doesn't meet the criteria, so it remains to be seen how prescient his analysis on this particular point is.
On the whole, however, trying to portray Scheuer as a defeatist or opponent of America is simply not the case - one gets the opinion that he's actually a little more bloody minded than our policy has been, and the book is actually a plea for more effective measures in our war with Bin Laden.