Yeah well where's the death certificpffhhhhahahahhhahaa
As for celebrating someone's death... honestly I figure while there is a genuine moral point there, justice is done more often by action than apathy. If the death of one guilty man spares the lives of many innocents, then I believe it to be a worthy kill as long as the guilt is proven beyond doubt. The sticky part is when relative standards come into it, but I think given it'd take more than a bit of awkward finangling to paint Osama in a good light, we likely don't need to get into the debate due to this specific issue.
And preserving innocent lives is something worth celebrating. Yes, his death arguably changes little, but it's something - he was one radical corrupt cleric among a sad multitude of them. The difference is he managed to pull something off, or so he claims. That's what made him a figurehead.