As Al Qaida leaders come and go, they'll all have the same idea to direct all of the group's focus on- trying to kill non-muslims and the countries they live in. 9/11 was a clever and brutal plan, undergoing years of development and killing thousands. With this new guy, will his supposed "innovative" plans kill even more in a shorter time? That's what worries me, really.
And besides, Osama Bin Laden has established Al Qaida moderately well, at this point, how much does charisma matter?