Yes, I'm on the side of Deckard being a replicant. I think it's a fantastic touch. If like Ford, you see the movie's message as the struggle of man versus machine, that detail makes no sense. However, I think it's about the nature of what it means to be human, and it makes the film much more powerful for me.
It might not be convincing if you're in the Human camp, but I always thought that since the escaped replicants were combat models (and they showed their, *ahem*, power levels at the beginning of the film), that it made sense that different replicants would have different abilities, especially if they were unaware of being a replicant, like with Rachael for instance.