I guess since you so kindly gave your personal testimony, I'll give one of my own.
My dad is fairly religious, but not very so. He never by force tried to make me religious, nor never limited my intellectual development in order to shield me from ideas that clearly were at odds with religious belief. He says he doesn't believe in evolution, but never tried to impart upon me that it was a lie, but just simply something he personally had a hard time believing. My dad was pretty moderate about it, and it's thanks to him and his wanting me to be as intellectually fulfilled as I could be that I've never been censured against my natural love of science.
However, he did makes us go to church every Sunday, still trying to distill into us some of his religious upbringing that his parents had instilled into him. When I was young, I found church to be boring and stuffy. I paid as little attention as I could, often reading books during sermons or sunday school. I gave very little of it heed, thinking it just some stupid waste of time that none of my friends ever seemed to be subjected to.
Then, as I grew older, and to be more respectful and responsible, I stopped reading during church and was too old to go to Sunday school. It was then when I finally started listening to the main service and sermons that I finally started to truly begin having doubts about the whole thing. Most of it was innocuous. I found the sermons boring and preachy, devoid of anything that actually seemed useful or interesting. They were never about hell or torment, but rather mundane stuff like being nice to neighbors and the like, stuff that had already been said a thousand times in sunday school, just in a much longer fashion.
What really began gnawing at me was the quotes from the Bible that they would say out loud during a certain part of the sermon. A lot of it was quotes from Jesus in the meek and humble fare, but every now and then they would say a quote that when I thought about it, scared me. I remember vividly the quote from Jesus which talked about how he was going to divide families, and bring the sword. That if you didn't love him more than you loved your parents or children, you would not be accepted (or something to that effect). When I heard these things, I thought it was immoral, and not to mention sounding very immature and selfish. But, when I saw how the rest of the church reacted to those verses, it filled me with dread. They were accepting it and believing it. My very own parents were affirming themselves to a book that said they had to love a dead man that might've never existed more than they could love me.
It was from there, that I really started looking through the Bible, really reading what some of it was about. I read the parts of the Old Testament in which God advocated, no, rather commanded the Israelites to commit genocide of a complete other people. And they were teaching this sort of stuff in Sunday school, to children, often with through the stories of David versus Goliath, and the walls of Jericho. It was only when I read the Bible did I understand how terrifyingly violent it could be, and how people were being brought up to accept it and even be happy with it. It was a very unsettling experience, to be amongst those people at church, seeing and hearing them be happy and acceptive of such stories and morals.
The story of Abraham and Isaac was particularly affective when I was younger, because it was taught to us in Sunday school, it was taught to us in sunday school, and my dad approved of it. It did me no comfort to have a father that thought happily of a story in which a father very nearly sacrificed his own son, just to appease some random whim of his god. Granted, I now will never doubt my father capable of such a thing, but at the time, it was revealing.
Combine that with violent level of fanaticism that religion has inflicted upon this world, I have a very hard time viewing religion as anything but detrimental.
