designer babies are here. human eggs can be selected based on whether or not a number genetic diseases are present and then inserted back into the mother. soon there may be genetic screening based on vision quality, height, intelligence, or whatever else they can come up with. perfect babies are around the corner. is this a desirable situation? well on one side of the argument humans have stopped their natural evolution because everyone is mating even the ones that would have died from a now curable disease. no longer are only the strong surviving. possibly people with poor vision would not be breading today without the advent of corrective measures such as glasses. they would have been an undesirable mate with all their bumping into everything and thus not bred with. if that happened then there would be no more people with poor vision. it's a light-hearted example but you get the point. but this natural evolution process is not taking place so one might argue that we need to screen our genes to further our evolution. diseases that would have been wiped out due to natural evolution (i.e. all the susceptible people would have died off) can now be screened out before birth instead of treating them with medicine later on.
for an argument against designer babies, it means that there may be a class war between less than perfect humans and genetically advanced groups of humans. people tend to group up and this may be another thing they group up on. people will also be less tolerant of human imperfections. would you rather marry a superhuman or an imperfect, genetically uncertain human? in time, more and more people may choose perfection if not from the start. look at all the plastic surgery that goes on for proof. also, the wealthy countries will have more genetically superior humans first and may start thinking of themselves as a master race and we all know where that can lead to.
so it's up to you. but i think there is a point in supplementing our stunted evolution but i would think human society couldn't handle it. maybe a very gradual approach would do it.