Yes, I do have a problem with it, but not because he was unarmed and not because it's not right. I don't want to comment on whether it's right or wrong because there's too much unpleasant details involved, and I'm certainly not the least bit sorry that this person is now gone. Most likely the world is much better off without him.
There's a greater issue. I think that Bin Laden and al-Qaeda are nothing. Their attempts to bring in the Western world have been pathetic. Almost every natural disaster that has happened recently has put them to shame. The only thing they've achieved, and that's very bad, is scare us, and make people play their game. They are full of hatred, they want the world to fear them and they preach and welcome violence.
And the problem is that we're only helping them. Not only are people throughout the world fearing terrorists and changing their lives because of that fear, but the US is involved in big military operations focused on killing a single Mr. Nobody, and then people are celebrating his death, by which they are only giving him and his legions more credibility. It's taking part of his game of violence, and inciting even more hatred in al-Qaeda and their followers.
And then there's the presumption of innocence. Sure, legally it doesn't apply here, this is war, and this is a military operation. Morally, you could still say it's OK. But in the eyes of the people, this wasn't just a military operation, this was an assassination because of the atrocities he's committed, it's a sentence and it's a form of revenge. I can't deny that even though I'm not from the USA, I'd hardly resist to put a bullet through his head. So, in a sense, that's an execution for a crime, and one that's made an example of. And we accept it like that, without a proper trial. In my opinion, this undermines the whole concept of the presumption of innocence, and the idea that no matter what a person has done, he has a right to the fair trial before a sentence is given. In a war situation you don't have the luxury to do this, but this is an exception in that it will be central in all news right after it happens. Mr. Nobody doesn't deserve to have a central news broadcast about a state-approved execution dedicated to him, no matter how legal or justified it was.
So, in short, I don't like what happened. I'm not saying I have an alternative I prefer, I just don't like what happened. There was a huge part of me that would prefer to live in a world that's a bit more principled, even if that means one more crazy guy full of hatred alive somewhere.
That said, there was also a part of me that was happy when I heard the news.