These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Anvilicious: A borderline case already. Definitely so had the director included the Coda included in the deleted scenes on the DVD.
Ho Yay: Vincent and Eugene. That scene after Eugene gets drunk, anyone?
Eugene leaves him a lock of his hair.
One-Scene Wonder: Tony Shalhoub has a few minutes as the underground contact who brings Vincent and Jerome together, helping and lending the equipment necessary for the fraud, and is brilliant as a genetic profile "used car salesman".
In a few short years, scientists will have completed the Human Genome Project, the mapping of all the genes that make up a human being. We have now evolved to the point where we can direct our own evolution.
Had we acquired this knowledge sooner, the following people may never have been born;
Of course, the other birth that may never have taken place is your own...
That's really not a solid argument. As the same could be said of any what if. If a person, who did great things, was born and became the person they were, as the result of rape, that doesn't mean that the world wouldn't be better off without rape. The way it is handled in the book still sucks though.
It's also a flimsy argument because the people in Gattaca are seen engineering their babies, not aborting them if they have defects. They wouldn't be quite the same people (which might make their stories less intriguing - is Ray Charles amazing because of his piano playing or the fact that he does it while blind?), but they wouldn't necessarily be dead.
To be fair it should also include some evil people who would not have been born as well. Especially if it turns out genocidal maniac is a genetic condition that can be spotted given this future level of knowledge.
It's not that the above necessarily wouldn't have been born, they just might not have those conditions which in many cases worsened their lives. Many other genetic conditions are fatal, so those without them would have a chance at life. True, it's possible having them in some cases is a trade-off (the well-known correlation Asperger's Syndrome and high intelligence, for instance), or merely through strengthening character, but one can't achieve much if they've died young from, say, progeria.
The reason Vincent couldn't be an astronaut. In the words of Cezary Jan Strusiewicz of Cracked: "If you have a condition that can kill you at any moment, common courtesy dictates you do not sneak into a profession where you're responsible for keeping a whole bunch of people alive. Whether it be here or on a super long flight through the cold, unfeeling vacuum of space. If Ethan slips away mid-flight to take a dump and his heart fails while he's sitting on the toilet, you've got a rocket ship full of future people that's going to smash into the nearest celestial body at about 15,000 miles per hour. There are some jobs you just shouldn't have, you selfish fuck."
Except it's never confirmed that Vincent actually has a heart condition, only that he has overwhelming genetic potential to acquire one. If anything, his feats of stamina seem to belie any heart condition. He's not perfect, given that scene in the exercise room, but we don't see him gasping for breath after a short run like Irene. The point is that the mere potential for having heart disease disqualifies him in a world of engineered people. As for the other point, he is a navigator, not a pilot and the best one in Gattaca at that.