I'd actually be surprised if LessWrong made many deconverts (though such people would be interesting to hear from, if they exist). The Sequences take atheism and a vague respect for rationality for granted, and focus on arguing about other topics. And the Sequences have shifted my beliefs around on some of those other topics, most notably Bayesianism.

The comparison to apologetics is more apt, I think, for sites like Rational Wiki, which Konkvistador aptly described as, "what a slightly left of centre atheist needs to win an internet debate... an ammunition depot to aid in winning debates."