Thanks. In most of those links, the author says that he gained some useful mental tools, and maybe that he feels better. That's good. But no one said that rationality helped them achieve any goal other the goal of being rational.

For example:

• Launch a successful startup
• Get a prestigious job
• Break out of a long-term abusive relationship.
• Lose weight (Diets are discussed, but I don't see that a discussion driven by LW/SI-rationality is any more successful in this area than any random discussion of diets.)
• Get lucky in love (and from what I can tell, the PUAs do have testimonials for their techniques)
• Avoid akrasia (The techniques discussed are gathered from elsewhere; so to the extent that rationality means "reading up on the material," the few successes attested in this area can count as confirmation.)
• Break an addiction to drugs/gambling.

... and so on.

Religious deconversion doesn't count for the purpose of my query unless the testimonial describes some instrumental benefit.

Carl's comment about the need for an experiment is good; but if someone can just give a testimonial, that would be a good start!