This war is a test ground for the Dumsfeld strategy of "smaller faster more flexible" forces. Turns out they have less flexibility because of limited troops on the ground to accomplish a growing number of different goals, e.g., in addition to facing the RG forces, there is protecting supply lines, taking out irregulars, clearing out cities we had hoped to bypass, and securing a nation the size of Texas to name a few. We just don't have enough troops on the ground to accomplish all that at once. Obviously that means a longer war (read: possibly a Summer war) because fewer forces must now acheive one thing at a time verses having enough to do everything at once. Thus the pause in ground force advance over the last week+.

I disagree with you that a larger force would move slower too. If they are designed to move quickly they could do that and wouldn't be slowed by having more reinforcements on hand. Logistics should not be a problem either as long as it was properly planned (read: we didn't have micro managing civilians overriding the generals and assuming the war would be over in a couple days).

There are certainly some disadvantages to having overwhelming force I suppose but none that outweight the risks of underwhelming force. As for Rummy the dummy, I think it's safe to say his plan has already proven unsatisfactory enough to see his head roll after this war is said and done.