I disagree with Peter Smith's contention that Deckard-as-Replicant is far more emotionally devastating than Deckard-as-human, if for no other reason than the fact that Smith suggests that this turns the movie into little more than a tired anti-technology screed. The replicants in the film--Beatty, Rachel, Leon, Pris--are all more human than Gaff, Bryant, and, yes, even Deckard himself. An emotional predecessor of the new Battlestar Galactica, the original Bladerunner suggests that the machines we create are ultimately more emotionally alive than their creators-- that as gods, humans are just as cold and distant as our own creator.
If instead we believe that Deckard is a replicant, what are we left with? A rather tired "trick" ending that belies everything we have seen up until that point: rather than a pointed romance between a human and a replicant, we have hot robot-on-robot action; rather than a replicant Beatty teaching the human Deckard what it really means to be alive, we have a robot saving another robot's life; and rather than a human Deckard rejecting his own kind in favor of the ones he was tasked with killing, we have a robot freeing itself from the shackles of its oppressors. Oh boy.
Let Ridley Scott do whatever he wants with his film, but don't try to convince us that these changes are uncontestably the work of genius or that those who prefer the emotional consequences of the original are somehow missing the point.