Here is a link to John Piper's answer to that question. (Found it via Randy Alcorn's quoting of it.) Piper's article begins with these statements:
In response to Osama bin Laden’s death, quite a few tweets and blogs have cited the biblical truth that “God does not delight in the death of the wicked.” That is true.
It is also true that God does delight in the death of the wicked. There are things about every death that God approves in themselves and things about every death that God disapproves in themselves.
There is much more to the article, but you will need to click through to see is explanation and Biblical support.
Another great resource on this topic is Andy Naselli's blog post titled Don Carson on Osama Bin Laden. (Don Carson is one of my favorite writers/speakers.) In this blog post Andy Naselli, of the Gospel Coalition, discusses a portion of the book Love in Hard Places by Don Carson. This post ends with this conclusion:
Therefore, in the present struggle, even while we must try to prevent the terrorists from doing more violence, we must eschew a vendetta mentality. Love demands that we do not demonize Osama bin Laden. He is a human being made in the image of God. He is an evil man, and he must be stopped, but he is a man, and we should take no pleasure in destroying him. Vengeance is the Lord’s alone. Do not offer the alternative, “Should we weep for Osama bin Laden or hold him to account for his genocide and prevent him from carrying out his violent intentions?” The right answer is yes.The rest of the article builds into this conclusion, so you should read the whole thing. Also, if you go there, they are offering a free downloadable copy of the book!