It strikes me that a common theme amongst the big atheists writing bestsellers nowadays (Hitchens, Dawkins, et al) is how much better the world would be if it weren't for religion. This seems, first of all, like a bit of a pipe dream, like pondering how great it would be if we were born with wings so we could fly around from place to place. Maybe true, but both groundedness and religion seem like endemic parts of the human experience to me, so we might as well get used to them.
Second, I'm not sure how this argument can be substantiated, with all this talk of rationality and such. It's easy to blame all the problems of the world on religion, since up until the twentieth century or so, the category "religion" was not really extricable from any other aspect of life. In addition to any of its more redeeming qualities, it was the main legitimator appealed to by pretty much anyone doing anything, and accepted by most people most of the time. Most things people did, they attributed to religion in one way or another, whether or not there was any validity to this and whether they believed it themselves. Further, the two great experiments in atheist social structures which history has, at long last, heaved forth for our consideration (fascism and communism) were pretty much unmitigated disasters from every possible point of view. It would be hard to find any religion-based system that could compete.
Finally, there is this weird faith in a better world, possible if only religion were eradicated. Where does this faith come from? There are certainly no empirical examples for it.
In the pretty good movie As Good as it Gets (from ten years ago already, how time flies), Jack Nicholson surprises a waiting-room-ful of people in his therapists office by questioning their quest for betterment: what if this is as good as it gets? What if there is no getting better, this is just the way life is going to be--it could get worse, but it's not going to improve.
Happily for his character, this was apparently not the case. But looking around at the world, I have to ask the atheists: what if this is as good as it gets? What if people just don't have the capability of acting any better than they currently do? What if you eradicated all religion in the world, and, John Lennon notwithstanding, people kept right on killing, dying, being greedy and hungry, and steadfastly refusing to live as one? What if it got even worse? And why wouldn't it?
Atheists also make a rather austere but lovely argument for believing in The Truth (meaning what they believe), regardless of whether it makes you happy or feel better or what-not. A pretty inspiring (whoops, poor choice of words) argument, but one which does little towards addressing what matters fundamentally to people, at their hearts--which can, for an awful lot of us, be said for atheism in general.