In Star Trek the genetically enhanced humans started a massive world war that almost wiped out humanity. That's what Khan was. In the Star Trek universe, genetic enhancement is illegal because of it (caused some problems for one of the characters in DS9).
I'm kind of shooting my own desires in the foot here, but that was a fiction.
We don't really have evidence for what happens when a generation of much-stronger, much-smarter than average humans are born, and subsequently give birth to another generation of even stronger even smarter kids. I'm hoping it's not a bunch of sociopathic Khans and that if we can figure out how to make smarter babies, we can also avoid making sociopathic murderous ones.
EDIT: On the other hand, I'm seeing the fear now - we create 100 of these superkids, and it turns out sociopathy is simply more fit than non sociopathy. They use their superior intelligence to out-perform "normal" humans, breed more of themselves, take over the world, and "normal" humans are gone.
Bad for normal humans, good for... whatever humans are after?
I guess it comes down to whether you're willing to accept that the continuance of some version of the human race is better than the potential extinction of all of the human race (which I believe is inevitable if we don't start making changes like this).
