Gattaca is a difficult and interesting movie. I find my feelings about its subject matter to be very much split between the positive and negative; while genetic manipulation provides great advances and has considerable potential, the movie makes clear the potential cost as well.
Two potential benefits of genetic engineering which the movie touches on seem of particular interest to me. The first is the relatively obvious one: reversal of our genetic stagnation. As our medical sciences have advanced, our ability to keep people alive and reproductively sound--despite genetic or physiological flaws which would have otherwise precluded survival--has increased. While this is undeniably a good thing, it has the unfortunate side effect of having effectively stopped our species ability to move forward on a genetic level. Genetic engineering circumvents this problem; Darwinism becomes artificial and consciously driven, but is at least reintroduced.
The other interesting side-effect of large scale genetic manipulation of humanity--and an attendant public knowledge about the basic realities of genetics--is that it renders the race issue essentially moot. Genetic differentiation between races today is essentially negligible anyways; what becomes important in society is not superficial differences, but quantifiable genetic ones.
Returning to the artificial Darwinism introduced by the movie; while in the long run it will be beneficial to the species, it is the inherent model of Darwinism, that few are winners and many are losers, so to speak, that is the cause of our protagonist's troubles. The fundamental question raised by the movie, for which I have no answer, is this: our species must change in order to move forward and survive. How many is it acceptable to sacrifice along the way?
In general, I find it difficult to reconcile the rate of cultural evolution with the rate of biological evolution in humans. In some respects, it feels like we're a bunch of 2 year olds who want to reach the cookies on the top shelf, constantly trying to find ways to stretch up to where we want our bodies to be.
Specific to Gattaca, and models similar to it--just because we can, should we? I can see the arguments for wanting genetically superior/disease-free people from a financial standpoint. Less medical costs, possibly less money "wasted" on employees who physically will not pan out in the long run, elimination of incredibly costly special education departments which are increasingly filled with severely disabled kids who previously died in infancy, etc. And I'm assuming the rocket missions are trying to find suitable worlds to terraform for the increasingly growing population, what with there not being the normal death rate anymore. But it seems like the space voyages, though frequent, are not permanent, and are a very small portion of the population, leaving an increasingly full-to-bursting earth. Unless there's a limit as to how many kids you can have, but there was never any indication of that as far as I noticed.
I guess what it boils down to for me is, just because we can, should we? I can certainly appreciate the impulse to discover. Finding out exciting shiny new things is, well, exciting. But in that excitement, I think it's very easy to not consider ramifications, or to devalue them. So my two cents is that we're better off taking things slowly and taking the time to examine the consequences of our actions as a species. As much as there is definitely merit in looking at the group over the individual, for the most part, as a society, we don't. Look at our government and the nature of complaints that people tend to have with it. Not saying I whole-heartedly agree with their decisions, but I think the very concept of deciding what is best for the group is something we find unappealing when it manifests, because as indivudals, we disagree.