A little knowledge instead of sci-fi speculation would be useful here!

They are simply using the cow egg as a bilogical vessel to allow stem cells to be grown from the human donor. The stem cells then be used for all sorts of treatments for the original human donor, a perfect tissue match to repair damaged organs and the like. The egg with the human DNA is NOT a viable embryo.

By the way I didn't hear anybody complaining about the use of human DNA in bacteria to create insulin. Maybe we should stop that before we get a superbug with arms and legs.......DUH!