[Siren]

What bothers me most is the fact that everyone is trying to manipulate the public in order to get what they want. The one side poses the question ‘whether the law should permit the creation of human-animal or chimera embryos’, which naturally makes people imagine unearthly human-animal babies, and of course they're going to answer "no". The other side mentions stem cell research and a bunch of horrible diseases they're trying to fight, and naturally the people will say "you go, beat that disease down!".
There is clearly a need for strict regulations on the issue, for example to ensure that this practice will be allowed only for stem cell research. In that case i think it would be ok since the embryo is killed at the blastocyst stage, when it's only a ball of cells. Of course this will open the door for allowing other things later, and a human-animal baby, a real chimaera, would be gross. Or with some other technique the result could be an animal bearing a human heart from your cells, still a human-animal cross, but in this case it would save your life and i'm not sure if you'd still think it's gross.
But, no matter how many regulations you make, a mad scientist could pop up anytime anywhere in the world, try to make a weird baby like that, and then let the world know. If he/she is at all successful, of course.