Won't matter for highly polygenic traits. For monogenetic disorders like Tay-Sachs, it will provide another line of defence along with conventional pre-implantation screening and pre-natal screening.
True Positive: non-viable, next embryo/round of IVF
False Positive: non-viable, next embryo/round of IVF
True Negative: Cool, parents move ahead with a healthy (in this regard) child.
False Negative: Parents move ahead with a false confidence.
Going in blind for muscular dystrophy, parents may hedge their bets by ensuring they live close to a school that can deliver against their childs needs, housing that is accessable (no stairs, easily accessable etc.), setting aside money for healthcare.
Of course the testing is only worse off in the case of a False Negative. I have no idea what the odds on that are, but I can imagine it'd be quite the shock for some people. In all I'm very bullish on the good IVF testing has the potential to do.