There's been a lot of bruh ha-ha on the interweb recently about Bin Ladin's death and whether or not Christians it should be pleased by it. So, I thought I would put in my two-cents on the matter.
Couple of thoughts.
First, wanting revenge is bad. Not only does Jesus says so, but I think it's fairly clear that the whole Bible is on his side (that's for those who think that Jesus came to give a new and nicer law!). David certainly doesn't take revenge against Saul, even though he has opportunity to do so. Even "eye for an eye, and tooth for a tooth" has to do with the working of civil government. God properly speaking is the only one can engage in retribution ("vengeance is mine says the Lord, I will repay"). This is because violations of justice are violation of his person as the Lord of creation. He gives justice's execution over to human agents (as in Genesis 9, where civil government is established), but this isn't revenge, but rather justice.
Justice is different than revenge because it represents the maintenance of order and the balancing of accounts. When it's done best, it generally speaking has nothing to do with the vendetta of the person executing it. Revenge is bad because it assumes self-justification, which is in fact the original sin. That's why Jesus says it's out. Not because he was a pacifist (he himself used violence in the Temple- remember!), but because taking revenge assumes that you are righteous and therefore injury to your person is worthy of payback. In other words, taking revenge assumes that you're owed something (rather than the God's own order of justice), when you're not. Properly speaking, only God's justice is owed something and therefore thinking that we are makes us into God.
The distinction between justice and revenge is an extremely important one and one which is often overlooked in our society. Liberal Protestants (and some Catholics) often appeal to Jesus' call to forgive enemies. This generally precludes wars they don't like. Then they forget all about it when there are wars that they do like.
This brings us to my second point: there's nothing wrong therefore with people wanting justice to be done. So being happy that Bin Laden was finally hunted down so that he can't kill innocent people anymore isn't bad at all. Neither would it have been bad to pray for that. It would be wrong to wish revenge on him. I think some (by which I mean a lot!) people felt that way (I wasn't one of them) and that was wrong and sinful.
When we move from the civil order to the realm of the order of the Church, I think we find the same thing. If salvation happens, it has to happen with judgment. That's why we have imprecatory Psalms. David wishes salvation and prays for it. If salvation happens, God has to judge the evil reality or persons (Pharaoh, Satan, etc.) that are preventing that salvation from occurring. There are other examples of this in Scripture- for example the cry of the souls under the altar in Revelation that ask for divine justice for the martyrs. So, the when the Church prays for salvation, it must also pray for the judgment of its enemies. There's no getting around this. This happened with both Egypt and Babylon in the Old Testament, as it will happen at the end of time for Babylon the Great (that is, the universal human society of the unbelievers).
Furthermore, that God's salvation comes with judgment does not mean that we ourselves escape judgment. The Church is merely the place where judgment as already taken place and the new creation has emerged. This judgment occurred on the cross and we participate in that judgment when we die and rise with Christ in the waters of baptism. Through this we have already moved beyond judgment. But let us be clear: our salvation only came with judgment and we were bought with a price.