Considering that Osama was a target, and their have been reports of him being on life support, it is likely he has not been leading anyone for some time. They probably had a new leader years ago, but kept it quite.
There have been much worse people than Osama, and there will always do. He is not the most dangerous, he is not the most cruel, he is not the most insane. Osama have been chosen by the media as the symbol of all the evil of earth, and now that he's dead a lot of people think that the good triumphed against the evil and stuff like that. But that's obviously not true.