Well, I regret how I phrased my answer. I read a lot of books about Buddhism and listen to a lot of monks explain things about Buddhism, and I really meant "all that stuff", i.e., tens of thousands of books and uncountable hours of dhamma talks about how to practice, what results to expect, etc.

To me the question was kind of like "is there really any evidence that this 'exercise' stuff is useful at all?" And the answer would be "yes... all the thousands of books about exercise and all the people who exercise regularly."