I'm sure there are many mixed emotions, and while I might not have reacted the way they did (the celebrating/dancing/rejoicing), I can understand the high level of emotions associated with those most intimately involved.

It's not on the same scale, but I live in OKC and went through the trauma of the Murrah Federal Building bombing in 1995. When Tim McVeigh was put to death the city felt a certain sense of finalization. We didn't rejoice publicly, but you could tell there was a sense of "it's finally over."

I don't think this is over (with the terrorists), but I can understand how those affected most intimately by bin Laden feel happiness and relief at his death.