With its massive population size comes r/Atheism's greatest strengths: there are always new jokes, news stories and anecdotes being posted, and the most popular ones often have hundreds of comments. And because of the voting system, the good content and comments (usually) rise to the top. With such a large and unfiltered group, one might expect a lot of dumb or ignorant people—and there are a few—but overall the discussions are intelligent and entertaining.
The biggest problem r/Atheism has is that too many of its top-rated submissions are on the shallow side: comics, Facebook conversations and the like. And of course, with so many like-minded people gathered in one place, it risks becoming an echo chamber that shuns opposing views. But the subreddit is at its best when raising awareness about some injustice or violation of church-state separation. For example, today someone posted about a teacher at his daughter's public school putting bracelets on students promoting an evangelism event, and redditors were full of supportive advice. When Damon Fowler was kicked out of his home for his atheism and activism, r/Atheism helped spread the story and contribute to his college scholarship. Its massive influence has even led to awesome stuff like a Q&A with Richard Dawkins.
It's true that r/Atheism tends to promote more fluff than I'd like. But there are always some interesting threads on the front page, and it offers a sense of community that no other place on the net can provide. Other related subreddits include r/AtheistHavens (for those who've been disowned for their unbelief), r/AtheistGems (a list of useful atheism-related resources) and r/Skeptic (which covers a wide range of superstition and pseudoscience). If nothing else, reddit is the ideal place for getting newly deconverted atheists to realize that they're definitely not alone.