Hussein Ibish:

For militant and extremist groups, defeat is disastrous, and this is an enormous defeat for Al Qaeda. The group's political fortunes were moribund following the rapid overthrow of the Taliban in Afghanistan, and were revived only by the ill-considered invasion of Iraq, which gave it a new battleground, rationalization and lease on life for a number of years.
The loss of this vital symbolic figure, no matter how impotent he had become in reality, will undoubtedly be another significant blow to Salafist-Jihadist ideology. They may have gained a martyr, but they've lost the image of a defiant leader able to combat the Soviet Union and America alike with impunity. His deputy, the Egyptian fanatic Ayman Zawahiri, lacks the charismatic appeal bin Laden had among certain extremists, and he has no apparent successor.
 On the other hand, Lawrence Kaplan warns against the American inclination to invest too much meaning into the death of any single bogeyman:

From Kaiser Wilhelm on, and for reasons that respond to needs unrelated to national security as such, we've always pinned the blame (and credit) for mass movements on their most visible spokesmen. Tojo, Milosevic, Saddam, and, on the flipside, Yeltsin or Aristide--George Kennan was right to lament the power of the bogeyman in American foreign policy. The persistence of nasty and divisive political impulses runs counter to our progress narrative, and also tends to be more difficult to explain. Rather, in accounting for the obduracy of certain countries and ideologies, presidents have advanced the proposition that, were it not for a handful of men like Saddam Hussein, the late Mohamed Farah Aideed, and Osama bin Laden, their supporters would eagerly sign on to the American program. "You think the Germans would have perpetrated the Holocaust on their own without Hitler?" President Clinton asked in reference to the bestial conduct of the Serbs in Kosovo. "Political leaders do this kind of thing."