A mass market written message would almost immediately turn off this site's core audience... I have two sites that have decently written, high converting copy. Both of them have been described by LWers as having great content , but too "salesy".
I think a better approach might to be just go with less copy, but more design that conveys the message. Think apple, but selling "smart and winning" instead of "hip and cutting edge".
I might try to put together a cool looking landing page that took this approach if there was enough interest.
It feels to salesy to me too and now I would like to understand this feeling better, namely why some people like and some dislike "salesy" things.
I think the idea is that I am used to judging the value of things for myself based on the technical facts. So a message like "THIS IS A VERY GOOD PRODUCT FOR YOU" is a turn-off. It looks like the advertisement is making a value judgement instead of letting me make it. Generally I respond best to advertisements that are strictly factual, even when the facts are obviously trying to be impressive...
I told an intelligent, well-educated friend about Less Wrong, so she googled, and got "Less Wrong is an online community for people who want to apply the discovery of biases like the conjunction fallacy, the affect heuristic, and scope insensitivity in order to fix their own thinking." and gave up immediately because she'd never heard of the biases.
While hers might not be the best possible attitude, I can't see that we win anything by driving people away with obscure language.
Possible improved introduction: "Less Wrong is a community for people who would like to think more clearly in order to improve their own and other people's lives, and to make major disasters less likely."