Well, I don't like the idea of entirely unfettered research re: messing around with humans, (raises some moral issues and I've likewise watched too many movies
) but it does have amazing medical potential.
What about, instead of eating that heart, it was used for a transplant? What if we could identify a gene in some animal that provides resistance to cancer or AIDS? Like I said, I'm not too comfortable with the idea, because we really aren't sure what the heck we're doing and where it might lead, but the positive possibilities are just as tremendous as the negative.
As for cross- ... um, breeding, fertilizing, gene-splicing?... whatever, between humans and animals, I think it's too early to jump up and down about it. A few human cells in an embryo is merely a minor step on the road to the type of biological disaster that will wipe out the human race for its misdeeds.
Note that I don't think we need any help in wiping ourselves out, be it alien, divine, or self-made biological entity. Unfettered greed and short-sighted policies are capable enough already.