I know the standard JW answer has to do with free will. Sure, the demons will eventually be destroyed, but only once it has been proven beyond all doubt that living Jehovah's way is the best way, otherwise men are only serving out of fear of God destroying them.
But that doesn't answer my concern. INNOCENT CHILDREN by the tens of thousands (perhaps more than 100 thousand) torn away from their parents in a tsunami in 2004 and being put through grave suffering and painful deaths in an earthquake in Haiti in 2010. If God is allowing suffering to teach us a lesson, isn't the price too high? Those children don't learn anything about God's love and the parents that lose them are not learning God's love. There is no excuse for not "snapping his fingers" and simply making that tsunami not exist or that earthquake not so severe. We could add the Japanese tsunami and past starvations in Ethiopia and endless events.
There are believers that can come up with answers for my concern and say that God didn't do it, but allowed it to demonstrate mankind's need of God. They say that God brings good things out of tragedy. God allows it so that humans can develop courage, devotion, loyalty, self-sacrifice, kindness, generosity, hope, trust. I don't accept that. The price is too high. If it weren't for children, I could almost let it be. But there you have it.