I see it as both. I'm atheistic, but honestly if it keeps you going day after day.....why is it not a gift? Keeping in mind plenty of problems erupt not from religion, but the extremists of said religion.
I suppose in conclusion, I see religion as a gift to people who need it to keep going. In general, it's a double-edged sword
Religion can either be a blessing, curse, or anything in between. I think it's usually a blessing due to the positive effects of spirituality, and the fact that it helps people deal with troubling times in their life if they believe it's part of a greater plan. In the end, it's whatever its followers make it into. The only real problem with it is when people get fanatically loyal to their tradition, putting aside the original message, and going out of their way to promote conflict.
I'm not religious. I don't believe in anything super natural or anything in the after life. And I think that we would have wars and blood shed with or without religion. There are good people and bad people. God knows that a Christian doesn't stone their neighbor because the Bible told them to. I'm a secular humanist and that means I live for people.
I'd say it can be either depending on the individual person and the particular religion. Religion helps some and hurts some. And there are so many different religions. Further, a religion that might harm one individual can also help another, depending on circumstances.
On a broader, societal scale, I'd say it's neither. I tend to think of side effect of how societies develop, perhaps even a necessity, rather than a blessing or curse.
I don't personally believe that religion is a gift or a curse and certainly isn't an excuse for war or violance. I believe that people, religious or otherwise, are all responsable for their own thoughts and actions regardless of the reasons they try to hide them behind.
great leaders who were atheists/lacked religion led the world into many violent wars, whereas many religious/religious hungry individuals lead the world into many violent wars. to shorten it even further, it's based entirely on the individual and their views on how to approach life, after all we gave a peace prize to someone who supplied millions with weapons, so, what mankind wants, mankind tends to get. regardless of the person, religion or otherwise, mankind will always want war regardless of the reason they are entering it. so, to answer your question, it is both a gift and a curse.