This is a topic that can be discussed forvever, and never answer the question...because I think it is impossible to build/field a vehicle that can do everything for everyone.
The bottom line in Iraq is that the war differs from one TF sector to another. What my TF saw as far as the threat, terrain, weather, etc...was different than the one 80km to the north, or the one across the Tigris from me, or south.
We lost tanks and a Brad to stacked AT mines in addition to the dozen or more HMMWV's coded out. These (the Hummers)were due to IED's and VBIED's. We saw bigger IED's as the tour wore on as the bad guys adapted. The point has been taken that you can armor a vehicle (or a soldier) to the point where it/he can't move.
About a million years ago I was in the 9th Infantry Division (Motorized) at Ft. Lewis, where we expected to die gloriously fighting the Russian hordes in unarmored HMMWV's and dune buggies (FAV's). It was said then, and I still believe:
If you can be seen, you can be hit. If you can be hit, you can be killed. Better not to be seen.
Damn true -
Would you like to see the Up Armored HMMWV replaced?
If so, what would you recommend?