On the other hand, we could point to Down syndrome eugenics: while it's true that Down's has fallen a lot in America thanks to selective abortion, it's also true that Down's has not disappeared and the details make me pessimistic about any widespread use in America of embryo selection for relatively modest gains.

An interesting paper: "Decision Making Following a Prenatal Diagnosis of Down Syndrome: An Integrative Review", Choi et al 2012 (excerpts). To summarize:

1. many people are, on principle, unwilling to abort based on a Down's diagnosis, and so simply do not get the test

2. the people who do abort tend to be motivated to do so out of fear: fear that a Down's child will be too demanding and wreck their life.

   Not out of concern for the child's reduced quality of life, because Down's syndrome is extremely expensive to society, because sufferers go senile in their 40s, because they're depriving a healthy child of the chance to live etc - but personal selfishness.

Add onto this:

1. testing for Down's is relatively simple and easy

2. most people see and endorse a strong asymmetry between 'healing the sick' and 'improving the healthy'

   You can see this in the citation in Shulman & Bostrom 2014, to Kalfoglou et al., 2004 - the questions about preventing disease get far more positive responses than for enhancement - and you can see in the quotes that the grounds for this asymmetry is not one of simple analysis or cost-benefit calculations, but one of values & politics and so is intractable

3. IVF is painful, difficult, and very expensive (see the comments in my sperm donation essay); as cryonics organizations know, intellectual support can be rather different from realized participants
4. the gain in income or accomplishment per IQ point is meaningful but highly probabilistic, delayed by decades, and accrues to the child or outsiders (through positive externalities) - not the parent; while we might expect returns to IQ to increase in the future as the US economy 'polarizes', the polarization would have to be very extreme for potential parents to experience active dread about their offsprings' prospects anything remotely like those who receive Down's diagnoses.
5. reproductive choices are most influenced by the woman; women in Kalfoglou et al 2004 generally are against such engineering, so that 28% is misleading, what counts is not the male support ~33% range but the female support in the low ~23% (Table 3.2, pg24) since they are the deciders
6. reproductive choices are also influenced by education & income; in this, the same table shows that the wealthier and better educated (those who can most afford and understand it) are not keen on embryo selection: support drops by 10% from the poorest to the wealthiest, and 5% from the least to most educated

Down's is the easy case, and many people still refuse it. To engage in IVF for embryo selection for some relatively subtle gains... I can't say I see it happening on a mass scale. At best, it might be tacked onto existing IVF procedures but the political/religious/moral concerns might block a lot of that. (Of course, a lot of people would want some level of selection if they were forced into IVF over reproductive problems but - homo hypocritus - they don't want to admit to wanting a 'designer baby', want to be seen acting towards getting one, or be known to have one; so a lot will depend on how well fertility services can spin selection as a normal thing or for preventing problems. Perhaps they could sell it as 'neurological defect prevention' or simply select without asking and count on people to quietly spread the word the same way that people spread the word about how best to signal one's way into the Ivy Leagues or where the best schools are.)

For mass appeal, it needs to be dramatic and undeniable: a genius factory.

28% is a pretty large number. I expect that in more abstract framings such as "improving general well-being" you would see larger rates of approval already, and marketing would push technologies towards framings that people liked.

I'm used to Robin Hanson presenting near / far mode dichotomies as "near mode greedy and stupid, far mode rational". But perhaps far mode allows the slow machinery of reason to be brought to bear, and most people's reasoning about IVF and embryo selection is victim to irrational ideas about ethics. In such cases, near mode (IVF is now possible) could produce more "rational" decisions because it bypasses rationality, while the reasoning that would be done in far mode has faulty premises and performs worse than random.