Not really sure what to make of it all.
I suppose there were 3 options; kill him, take him hostage, do nothing.
It's a mercy that he was killed the more I think about it (imagine the amount of hostages taken in to demand an exchange). Although I disagree with violence on principle I think it's better to do something than nothing against terrorism. It does defeat that air of invincibility and eternity about him as a leader (the latest tapes have all had the same underlying taunt: "hey, I'm still alive lol". Although perhaps it's not idealistic, the world is probably a better place without him. It also raises important questions about Pakistan's security.
And the counter argument is what everyone else has been saying: it doesn't really achieve much. People have described him as the "head" of terrorism; he wasn't even that, he was the face. The brains and strategists behind the 9/11 attacks are still at large. Also, fighting murder with murder, being provoked by Al Qaeda's actions, the potential problems with Pakistani relations, the potential for retaliation by the terrorists.
The biggest problem I have with all of it is the fact that people are celebrating assassination. And the outdated american policy of fighting ideology with weapons. Even then, I think it's a step in the right direction.