Personally, I'm not particularly bothered with Rumsfeld's use of a machine to sign letters to the family of dead soldiers, nor necessarily by the apparent failure to provide enough armor (which may or may not be the case).
In the first case, this is what often happens, it may symbolically show a lack of concern for the troops, but (a) it has little practical effect, and (b) and it may become necessary if we wind up losing a lot of people in the war quicker than we are now.
In the second case, if we are low on armor (according to Hack Kelly, the armor situation isn't as grave as we have been told (although it should be noted that in the article, he only refers to the 278th Regimental Combat Team of the Tennessee Army National Guard's vehicles, and ol' Hack Kelly has been known for saying things that are gross misinterpretations of the situation.
A few more examples, and here.))
this could just be a normal snafu or a miscalculation as to the enemy we would face.
I don't expect Rumsfeld to be prescient or to think of all possible scenarios. Nor should he micromanage everything or be put up as responsible for everything that goes wrong in Iraq; his job isn't managing every detail, it is managing the war as a whole.
The problem is that he got that wrong.
What I do fault him for is ignoring the generals, ignoring anyone who didn't trust Chalabi, and going in with too few troops and expecting the Iraqis to greet us with open arms and to eagerly accept us remaking the society as we see fit.
Even the relatively-friendly Shiites have stood up against us; the reason for these elections rather than sham caucuses where Chalabi was installed is because the Shiites threatened to revolt.
Everyone who knew anything about the region or who was actually in the active part of the military (i.e. not the civilian leadership) thought that Rumsfeld had a bad plan.
That is the problem. Rumsfeld is arrogant, didn't listen to anyone, and went in with a flawed war plan.
Rumsfeld got the war as a whole wrong. Remembering that is more important than nitpicking over details he got wrong.
That is all.