The problem, though, is that what the rationalists will probably conclude is "there's no solid evidence, and it seems likely that any advice works well for a subset of the population and hurts other subsets of the population. You should quantify yourself and experiment."
Which is advice that people are going to have a hard time taking. Giving up specialization of labor is rather hard and rarely worth it.
Now, they might find a few gems- like "you should figure out diaphragmatic breathing"- but it'll be hard to separate those from fads or overbroad advice ("this diet agrees with my evolutionary views, thus I suspect it's good for everyone").
I think even this would be pretty useful; it basically means 'we don't know anything of use; average person should ignore this field for at least 10 years'.
Holden Karnofsky of GiveWell.org interviewed Jasen Murray of SIAI and published his notes (Edit: PDF, thanks lukeprog!), with updates from later conversations. Lots of stuff to take an interest in there - thanks to jsalvatier for drawing our attention to it. One new bit of information stands out in particular: