To elaborate... prior to reading TSG, I thought of myself as an atheist, but I held open a (very) small amount of willingness to consider the idea of some sort of creator, mainly because I'd not heard a convincing counter to the "irreducible complexity" idea. After reading TSG, I felt convinced that there is a reasonable way for, say, the eye, optic nerve, etc., to evolve, that doesn't require the entire thing to appear at once.
Once I crossed that hurdle, I felt a lot more confident in publicly declaring myself an "atheist" instead of just saying "agnostic" which always felt like something of a weasel term.
Of course, having grown up in the "Bible Belt" and having many family members who are devout Christians, this led to some interesting, erm, "discussions" over the years.
I also appreciated TSG for introducing me to things like the Iterated Prisoner's Dilemma and the works of Robert Axelrod, Robert Trivers, etc. and ideas like "kin altruism", "reciprocal altruism", etc. A lot of things make more sense after reading that book.