As always, Marc Lynch's analysis of Obama's speech is worth reading:
[W]hen things don't go their way, will they really follow through on their promises to draw down? Few people believe that. And if they don't believe it, then the mechanism of pressure doesn't operate. So it seems to me that the best way for skeptics such as myself to help this strategy to succeed is to keep a sharp focus on the proposed mechanisms of change, demanding evidence that they are actually happening, and to hold the administration to its pledges to maintaining a clear time horizon and to avoiding the iron logic of serial escalations of a failing enterprise.
Amen. And will do.