It seems to me that the LessWrong rationality does not concern itself with the computational limitations of the agents, using as normative the idealized model that ignores limitations, and lacks extensive discussion of comparative computational complexities of different methods, as well as the security of the agent from deliberate (or semi accidental) subversion by other agents. (See my post about naive agent)
Thus the default hypothesis should be that the teachings of LessWrong for the most part do not increase the efficacy (win-ness) of computationally bounded agents, and likely decrease the efficacy. Most cures do not work, even those that intuitively should; furthermore there is a strong placebo effect when it comes to reporting of the efficacy of the cures.
The burden of proof is not on those who claim it does not work. The expected utility of the LW teachings should start at zero, or small negative value (for the time spent, instead of spending that time e.g. training for a profession, studying math in more conventional way, etc).
As intuition pump for the computationally limited agents, consider a weather simulator that has to predict weather on specific hardware, having to 'outrun' the real weather. If you replace each number in the weather simulator with the probability distribution of the sensor data (with Bayesian updates if you wish), you will obtain a much, much slower weather simulator, which will have to simulate weather on a lower resolution grid, and will perform much worse than original weather simulator, on same hardware. Improving weather prediction within same hardware is a very difficult task with no neat solutions, that will involve a lot of timing of the different approaches.
It seems to me that the LessWrong rationality does not concern itself with the computational limitations of the agents
The LessWrong community is made up of a lot of people that concern themselves with all kinds of things. I get annoyed when I hear people generalizing too much about LessWrong members, or even worse, when they talk about LessWrong as if it is a thing with beliefs and concerns. Sorry if I'm being too nit-picky.
Someone who claims to have read "the vast majority" of the Sequences recently misinterpreted me to be saying that I "accept 'life success' as an important metric for rationality." This may be a common confusion among LessWrongers due to statements like "rationality is systematized winning" and "be careful… any time you find yourself defining the [rationalist] as someone other than the agent who is currently smiling from on top of a giant heap of utility."
So, let me explain why Actual Winning isn't a strong measure of rationality.
In cognitive science, the "Standard Picture" (Stein 1996) of rationality is that rationality is a normative concept defined by logic, Bayesian probability theory, and Bayesian decision theory (aka "rational choice theory"). (Also see the standard textbooks on judgment and decision-making, e.g. Thinking and Deciding and Rational Choice in an Uncertain World.) Oaksford & Chater (2012) explain:
Is it meaningful to attempt to develop a general theory of rationality at all? We might tentatively suggest that it is a prima facie sign of irrationality to believe in alien abduction, or to will a sports team to win in order to increase their chance of victory. But these views or actions might be entirely rational, given suitably nonstandard background beliefs about other alien activity and the general efficacy of psychic powers. Irrationality may, though, be ascribed if there is a clash between a particular belief or behavior and such background assumptions. Thus, a thorough-going physicalist may, perhaps, be accused of irrationality if she simultaneously believes in psychic powers. A theory of rationality cannot, therefore, be viewed as clarifying either what people should believe or how people should act—but it can determine whether beliefs and behaviors are compatible. Similarly, a theory of rational choice cannot determine whether it is rational to smoke or to exercise daily; but it might clarify whether a particular choice is compatible with other beliefs and choices.
From this viewpoint, normative theories can be viewed as clarifying conditions of consistency… Logic can be viewed as studying the notion of consistency over beliefs. Probability… studies consistency over degrees of belief. Rational choice theory studies the consistency of beliefs and values with choices.
Thus, one could have highly rational beliefs and make highly rational choices and still fail to win due to akrasia, lack of resources, lack of intelligence, and so on. Like intelligence and money, rationality is only a ceteris paribus predictor of success.
So while it's empirically true (Stanovich 2010) that rationality is a predictor of life success, it's a weak one. (At least, it's a weak predictor of success at the levels of human rationality we are capable of training today.) If you want to more reliably achieve life success, I recommend inheriting a billion dollars or, failing that, being born+raised to have an excellent work ethic and low akrasia.
The reason you should "be careful… any time you find yourself defining the [rationalist] as someone other than the agent who is currently smiling from on top of a giant heap of utility" is because you should "never end up envying someone else's mere choices." You are still allowed to envy their resources, intelligence, work ethic, mastery over akrasia, and other predictors of success.