In Iraq, the three primary means of attack are RPGs, samll arms, and improvised explosive devices (IEDs). The armor was already good enough for the small arms (haven't heard of any heavy MG attacks). The armor was probably all right for IEDs (normally "off-set" & detonated as a vehicle drives by) as well--it certainly will be with the armor up-grade. And the grill should neutralize RPGs. All good stuff.
The problem is, the Strykers are very seldom going to be attacked. Combat units in Iraq now, even in HMMWV & 5-tons, are not being hit. The Iraqis have already figured out the difference between our logistics & admin traffic versus our combat arms guys. When attacked, combat arms units immediately counter-attack and do all they can to pursue, hunt-down and kill the attackers. The support elements simply try to break contact. A convoy of trucks carrying an infantry company can roll down a road untouched while a logistics convoy 5 minutes later on the same road gets hit hard.
It'll be interesting to see what tactics the Stryker guys use to defeat that threat.
Scouts Out! Cavalry Ho!