A chilling story from Science Daily. I remember when Britain authorized the production of human-animal hybrids (sometimes called "chimera", NPR has a story from 2007).
Of course, these are not true hybrids. They are taking the nucleus from a human cell, and placing it into the egg of an animal. This is just human cloning, using an animal cell as the "structure". The animal cell contributes zero DNA (although the mitochondrial DNA is from the animal).
The primary danger of this research (besides the risk of creating an army of half-men/half-cow overlords!) is the notion that these embryos are somehow "not human". Then, it will be ok to destroy them.
The Science Daily article has shown this research to be a failure. We can be thankful.
The article reveals one of the unspoken problems with ESCR. The availability of human eggs.
You see, even if some miracle treatment were possible with ESCR - there are not enough human eggs to make it widely available!