Blackfive gathers some initial reactions.
If any passersby are unfamiliar with Petraeus, I recommend Rick Atkinson's book, In The Company Of Soldiers. (Which, *koff* I reviewed on my amazon page) He, along with the other commanders of the 101 Airborne during the invasion of Iraq are acutely and sympathetically portrayed therein.
I hope it works. He's a splendid soldier, and if we fail in Iraq it won't be because we're not sending our best.