The reality is that people already choose the genetic makeup of their child by choosing the genetic quality of their mate. People with bad genes don't reproduce as often, although nowadays, someone with serious defects can probably accomplish it due to the size of the population, modern communications (for finding others like you, or that one person with a fetish), and social welfare.
But ask yourself this (assuming you want children): Would you choose a mate who you 100% knew were going to produce a child that was: lower IQ, unattractive, or shorter lifespan?
Our standards of beauty are geared towards people who are: well fed/fit, intelligent, and have the exterior appearance we desire of our children (hair color, eye color, etc.) My wife definately wants our child to have "big eyes" and a big nose, someone many chinese/japanese/koreans often have cosmetic surgery for (put an extra fold in the eyelid, for example. She would also be especially pleased if the kid has brown/blond hair and blue eyes (98% chance it ain't gonna happen since she carriers no blue/green genes).
Think most women want a man with slurred speech? Do you most people think a limp is sexually attractive? (BTW, I said this as a member of the set of those unfit, homely geektypes)
Direct genetic manipulation is just a more deterministic way of accomplishing what people already subconsciously desire in their breeding patterns: the most intelligent, fit, attractive offspring.
Of course, the usual canards will come up "OHMIGAWG, what if everyone chooses a boy! The end of the species!" (I personally prefer girls over boys). GM discussions usually turn into discussions of monsters, eugenics, "what if they clone/produce the next Hitler/Khan", and whatever nightmare scenarios you can conjure up. It's hard to convince people's minds otherwise. It just takes a generation. There was similar opposition to organ transplants, blood transfusions, even surgery, when it first became available.
