Regarding IED vs MRAP, my opinion is that from the insurgents' POV, it's another victory for them. They have succesfully forced the US to spend extra gazillion dollars to upgrade their vehicles and protect their supply lines. And for a freakingly tiny portion of that money, they can adapt to keep their leverage, either by building even larger IEDs, manufacturing/importing EFPs, and/or devising new tactics. The (crude) cost/expenditure analysis is in favor of the insurgents.