1. Killing senior leadership is a slow road to victory (Except in a case where some guy with legal power over people is forcing them to do things against their will. UBL's power is the power of the conditions he exploits, the power of his cause, and his supporters are all volunteers.) Killing him will not weaken the cause, but could make it stronger.
I agree in the case of a persistent COIN or CT campaign. I see it differently with UBL. His death would create an immediate shift in how the West chooses to counter AQ. He's a big symbolic target for the U.S. and one of the main justifications for being in Afghanistan. I don't think it would make AQ stronger either, but do think the result would be more attacks as followers compete to emerge the new leader.

2. Capturing him and attempting a civilian trial under US, or even international, standards would be an IO disaster for the west.
Agree, I sure hope they wouldn't take him alive.

3. He will be replaced. Take out UBL, and AQ gains a new leader who may actually be more effective than the current one. Take out AQ and a new organization will form that may well be more effective than AQ.
Really good point, I am curious how this will play out. I expect it will happen eventually, and maybe even soon.