The thing I've wondered is, if Deck is a replicant, how long has he been activated? Is all of his past with the police false, or has he been around for a while? Some have speculated that he's a malfunctioning replicant or a special model designed to help police the ranks of the other replicants.
Deck does exhibit many more human qualities than the others around him, just look at his approach to the job versus Holden. But if you follow along the reasoning that replicants act more humanely than actual humans and that Deckard finds this disturbing when he is having to retire them, finding out that he himself is one uproots his universe completely and makes those lingering sympathies ring true. Human or replicant, it makes sense but to me the replicant notion compounds any of the ideas.
I wish the Tyrell reveal scene had been filmed. The idea that Tyrell would be revealed to be a replicant and Roy finding the preserved hibernated corpse of the real man deep in the building sounded fantastic.
I could just discuss this film all freaking day. Just got the DC and International Criterion LDs and can't wait to get them fired up.