I am sort of a non-religion-specific kind of person, and I generally don't have a problem with people who decide that the whole God thing is bunk (as long as they don't spend too much time trying to convert me). To each his own, and all that.
The one thing I've heard atheists I know say on occasion that strikes me as being utterly ridiculous is that "people would be nicer to each other if they didn't have religion" or "... if they knew they only had this one life" or some such. I don't believe in original sin, but I do believe that a lot of people are just plain mean and miserable by nature. Some religious people are mean and miserable, but some people actually try to overcome their wretched personalities in order to be better people because of religion. And some of those angry and unpleasant religious folks would be just as horrid without their religion as a focal point. They'd find something else as a focal point for their nastiness.
Perhaps they'd get involved in party politics, which is an awful lot like religion in many respects (and in bed with religion a little too much here in the US, if you ask some people).