No, it is not completely bomb proof. What is? (BTW, Wouldn't an IED with 500-1,000 lbs. of explosives be rather large and easier to spot?) Anyway, the point is, we're doing something about the biggest threat our troops face and we are seeing success, however slowly that may be.
It certainly raises the ante, but the VLIED (Very Large IED) are, in fact, the big killers today. They will take out anything, up to and including an M-1 Tank. They are concealed in drainage pipes underneath roadways, or in another technique - pour gasoline on the asphalt roadway, light it. Then scoop away the soft asphalt, dig a hole to bury your IED and then recover with asphalt. Wait for patrol.
I'm not trying to badmouth the Cougar. I wish we had more, but I'm just tired of hearing gutless politicians use something like the Cougar to attack the military because every supply clerk and chaplain's assistant doesn't have his own personal Cougar.