(6) One of the benefits of the previous point is that it introduces the vocabulary needed to clearly express one of atheism's oft-forgotten selling points over religion. If atheism and religion are products available for sale in the marketplace of belief systems, and if faith is the currency human beings use to make purchases from this market, it's worth pointing out that the frequency of "buyer's remorse" is orders of magnitude lower for atheism than for religion. I draw this conclusion not from anecdotes, but from the fact that religion seems to have developed (to mix metaphors) an "immune system," one that atheism completely lacks.
There is an entire body of theological literature that has accrued over the centuries dedicated to the sanctification of the crisis of faith. Religious believers -- clergy and laity alike -- approach their religious superiors and say, "I've really been troubled lately. I feel like my faith is slipping away. I have to struggle to keep in touch with the Lord, and even then I feel so distant from Him." Only a belief system that has been down this road many, many times before would respond the way religion does: "That's wonderful. I know it's hard to believe, but this is actually proof that your faith is strong. You may feel like despairing now, but you will get through this dark time, and you will be renewed, your faith more robust than ever." According to religion, doubt in one's faith is like one's scalp tingling while using Selsun Blue: that means it's working!
(Interesting that the converse is never the subject of exhortation on the part of religious authorities. When was the last time you heard a rabbi or an imam or a priest or reverend delivering sermons castigating those whose faith is utter and complete, with all trace of doubt safely dispatched beyond the horizon? Where are the Baptist preachers warning their flock not to rest on their laurels with the complacency of certainty, to hurry up and start doubting, to plunge headfirst into that dark night of the soul, to embrace the benefits that such spiritual suffering brings?)
Contrast this with science. There are comparatively very few cases of a biologist approaching his physicist friend and saying, "Bob, I gotta tell you, lately, I've been wrestling with my belief in the scientific method. It just doesn't speak to me the way it used to. Sometimes I doubt it can live up to the promises it's made." Science has never needed to develop such a vast body of apologia, such an immune system, because it's never experienced such a widespread infection.
I readily concede that religions are not the only products in the marketplace of belief systems to have been "returned for a refund"; certainly there have been high-profile atheists who have converted to Christianity or other religions. But they are few and far between compared to the number of religious believers who experience buyer's remorse every day.