There are five things you need to build a great society:
1. Economic Surplus
2. Principled Military
3. Constitutional Government
4. Leadership that serves the people
5. Moral Code
Every single empire in human history have risen because of those five traits, and every single one has fallen because one or more of those went into decline. There are no exceptions.
Religion deals with Moral Code. People need something more than the government and men to feel accountable for. Even for you atheists out there, unless you're a pathological killer or were raised really messed up, answer to some sort of higher authority. We're all taught not to kill. Why? Well, because it's wrong. Why? Because God said so, or barring that, it simply is. If you took a completely darwinist approach, then it's the logical thing to do to, say, kill any political candidate you don't agree with to protect your views. I mean if everyone lived completely logically, what's to stop you? If no one answered to some sort of higher authority or drew the line of what is right or what is wrong simply because then this is what it would all boil down to.
Now you could make the argument that people could believe in these things simply for the betterment of society in general, because order would lead to prosperity for everyone. But what keeps you from killing someone if you're smart enough to get away with it? Or stealing if you're smart enough to get away with it? Well, not much if you don't believe some things are wrong to do simply because they're wrong to do.
Also, if you didn't have religion, you wouldn't have the iPod. I'm serious. Christianity laid down the foundations for Western unity and industry. The power of monotheistic religions is a much stronger galvanizing force than something like Buddhism. Why do you think there were so many Crusades? And if it wasn't for the Crusades, those European troops returning from the Holy Land would've never returned with classical texts that were lost during the Middle Ages after the fall of Rome but preserved by the Muslims. That sparked the Renaissance. Religion inspired millions and millions of people in every human endeavor including literature, art, engineering, botany, exploration, medicine, etc. They were all concerned with trying to unravel the mysteries God implanted in the universe. That was their drive.
I'd say it's brought more good than harm.
Also, the music is killer.