Some quick points:
We must keep in mind that God is the ultimate judge, not us
Take heart in the fact that no more acts of destruction will come from this man again. This is made possible by his death, but could have also been a result of a death to the evil in his heart through conversion. Remember that Saul also persecuted and killed many. However, he was shown the err of his ways and accepted Christ into his heart. Paul became one of our most prolific authors in the Bible. Osama (Usama?) could very well have been extended the same Grace that God has extended us. Some hearts, though, remain hardened even in the presence of the Lord.
And lastly, God has the power to forgive all sins if He is given the chance. No sin or streak of sins is too great for Jesus' blood to cover. Saying that Bin Laden is/was beyond redemption is to limit God's saving power.
At this point, it's between him and God. We can rejoice in the knowledge that evil will no longer come from this man.