A place to post my opinion, eh? As if most of you don't already know what it is, but okay...
I think religious belief is a delusion. It seems to be one the human brain is hard wired to fall for, and one all human cultures have approved of, every culture has invented a pantheon of usually supernatural good and evil agents that have to be dealt with in various ways. I've always liked Christopher Hitchens' characterization of religion as our first and worst attempt at explaining the reality we find ourselves in. We're so focused on pattern recognition that we'll see patterns even where there aren't any--just look up at the random scattering of stars in the night sky, every culture has found patterns there--and attribute agency to pretty much anything that moves, and I'm inclined to think that that plus our obvious need to find explanations for things, and our tendency to invent one when we can't find one any other way, is the source of the delusion.
For myself, I find the evidence and arguments offered in support of religious claims to be simply insufficient to justify accepting them as even provisionally true, quite apart from the fact that they fly in the face of everything I understand about how the world works. That is perhaps a consequence of a good scientific education, I didn't arrive at the atheist position until I was well into my 30s. I came from a deeply religious household and never really thought much about the truth or falsity of religious claims before that, they were just part of the background of my life and I took for granted the lessons learned at my parents' knees, so to speak. Then a number of deeply affecting events in my personal life brought them to the front of my mind and I began to examine them with the analytical tools I'd learned and worked with at university and in the jobs I'd had, and found that they just didn't stand up to skeptical scrutiny. So at about the age of 35 I arrived at the atheist position, which is to say, I concluded that religious claims about the nature of reality and the meaning and purpose of it all deserve on the evidence to be rejected. It's like Kakato said, in a ground blizzard at the Arctic circle in January, you better rely on yourself, you can't just sit there and ask some supernatural being to rescue you. I was never in a situation as threatening as that, but I've been close enough that I think I understand what he means.
And one day I heard Sam Harris talking about these things. Around the world, 9 million children under 5 years old die every year of starvation, malnutrition, disease, and violence, often in great pain and terror. Do the arithmetic, that's about 17 every minute. Their parents, mostly believers in some deity, will be praying for their children to be saved, and their prayers will not be answered. I simply cannot believe in a deity who routinely allows avoidable suffering, particularly of such innocents, to exist on that scale. Far as I can tell, no prayers are ever answered. Given all that this supposedly just and loving deity does not accomplish in the lives of so many, despite their desperate prayers for help, it seems extremely improbable to me that he exists at all, and certainly is not to be counted on in a crisis.