The armed drones the CIA has been flying over Pakistan didn't kill Osama bin Laden, but drones undoubtedly played a key role in finding him, preparing the way for the raid that got him, and conducting the raid itself. The controversy over the CIA's drone missile strikes in Pakistan tends to obscure the fact that the main role of unmanned aerial vehicles in this war has been to act as a nearly undetectable eye-in-the-sky that can circle a target area for hours on end. In addition to weapons, these aircraft carry video and infrared cameras, radar, and devices that can intercept electronic communications.
All this makes them ideal for what is called "forensic intelligence," in which analysts review the video and other data drones have gathered over days or weeks and use it to work backward in time, tracing the comings and goings of known or suspected terrorists. The Predator drone was used in that way to track down bin Laden follower Abu Musab al-Zarqawi in Iraq in 2006, and helped guide the fighter planes whose bombs killed him. The details of how drones were used in the operation that killed Osama bin Laden may take a while to come out, but it's a good bet they played a major role in it.