Limiting the scope of U.S. objectives is an important step in the right direction.  Still, I see two principle shortfalls with the Obama administration’s “new” strategy for Afghanistan and Pakistan:

1. Rosy assumptions on Iraq drawdown:  The plan miscalculates by underestimating the risks associated with the drawdown of U.S. involvement in Iraq.  Should a violent faction lie in waiting for the U.S. to pullout (now they have the timetable and can do so) and the situation in Iraq deteriorates, how does this affect the planned troop increase in Afghanistan?   The probability of such a contingency is not as unlikely as some would have you believe.  
2. Inadequate troop levels given historical ratios:  If you accept the view that 1) disrupting, dismantling and defeating al-Qaeda in the Af-Pak region is a top priority U.S. national security objective, and 2) that we have neglected Afghanistan in terms of troops and resources, then it seems to me as though a measly 4,000 trainer and 17,000 combat troop surge is hardly enough.  Some have suggested five brigades but given the difficult terrain, I think it might take even more.  See this RAND report for historical force-population ratios for counterinsurgency campaigns.