Dumbledore lives. I kinda thought that he had horcrux. But am now convinced that he and Snape staged the death scene. There may have been a silent expelliarmus curse hidden behind Snape's killing curse that threw Dumbledore off the tower. The killing curse doesn't knock people around. Look at "Proof: Dumbledore not dead" there's an article there with more detailed proof that Dumbledore staged his death.

I think that Dumbledore was pleading for Snape to kill him right then, because he knew that Snape did not wish to perform the killing curse on Dumbledore (masked or no) its a dangerous curse to fool around with. Though not dead Dumbledore must have been badly injured. That fall itself could have been fatal. Kinda like Gandalf's fall in LOTR as he fought that balrog.