The procedure in question is called mitochondrial manipulation and addresses children in danger of being born with mitochondrial disease. This disease results in infected mitochondrial DNA being unable to convert food into energy causing various parts of the brain and the body to malfunction.
Essentially the process would include taking the nuclear DNA from the father and mother and the mitochondrial DNA of a female donor; the result would be a child born with the genetic material of three different people. The process could save the lives of thousands of children born each year with this debilitating condition, however there is no way to predict potential long term side effects of a procedure which changes the DNA of every cell in the body (with the exception of red blood cells.) And if there are negative effects, those effects will be passed down to decedents.
This procedure may be the first step in our ability to completely engineer our ideal human. Are their moral or social implications to such abilities? Does the fact that we CAN do something mean we SHOULD do something? Perhaps only time will tell..