Sure, the first thought most people have, consciously or subconsciously, is "Would my parents have kept me if they'd had this option?" and the whole concept thus makes us very uncomfortable...
However, looking at humanity as a whole and taking into account that we pretty much switched natural selection off... can we actually afford not to do this?
I mean, billions of sperm and thousands of eggs never get to be a fertilized anything. Of the fertilized eggs, about a third or so actually manage to become a clump of cells trying to become an embryo and of the actual embryos, quite a few never make it any further. Choosing them for looks isn't very ethical, seeing as look are very much dependent on the current fashion, but physical fitness and intelligence aren't quite the same thing. Seeing as most 'potential' human beings never make it, I don't quite share the moral dilemma in choosing the best of the best.
Raising not only humanities average intelligence but much more importantly the lower end seems a phenomenal gain to me.