I'm a solid atheist, through and through, for too many reasons to list. I'll go through several of my major reasons, aside from my views on science.
Some understand religious texts metaphorically, others understand them in literal terms. If faith in a religion makes you a better person and improves your quality of life, great. As long as you're not bothering anyone else, I don't see anything wrong with believing in any deity. However, in this world, that is seldom the case. I don't mean to say that on an indiviual level, religion is bad, but on a global scale, I would assert that. Religious conflict has plagued humanity from the very start. Even within practically every major world religion, you find problems and hypocrisy.
To me, religion is a human creation. Humans came up with the concept of dieties, humans wrote the religious texts, and humans changed religious practice as society evolved. Take a look at Christianity, for instance. Surely, few people today would claim that reading the Bible, the most reproduced book in existence, is sinful, yet several hundred years ago, you could be burned at the stake in the name of God for reading it if you weren't of the priestly class or distibuted it to peoples of the non-priestly class. There's a ridiculous amount of this sort of stuff all throughout the Bible and other Christian texts if you choose to look closely at it. Western religion especially is more a reflection of the times than anything else. Why are there also so many different religions when, according to their adherents, they're all the "correct" religion?
I also tire of hearing the agnostic arguments, particularly when used in the context supporting the existence of a divine entity or the supernatural. Of course, we cannot know beyond the shadow of a doubt whether a deity exists. But if I were to say that super-evolved, invisible giraffes living in space came down once a weak and adbucted a human being to feast upon, you'd probably think I was just making things up. But who's to say they don't really exist? After all, you can't prove that they don't exist. Likewise, you can't prove that vampires or brain-eating zombies don't exist, so therefore we must treat them as though they do exist, just in case. If we are to treat them as though they exist, though, shouldn't the burden lie on me to prove their existence? Likewise, if you're going to try to shape the world in which I live and tell me how to live my life (according to how God would want), then the burden of proof is on you to show that said God exists. A lack of evidence for something's non-existence is not proof of its existence.
All that being said, I apologize if I came across as being harsh or rude. I am not making any personal or character attacks. I am merely stating why I believe what I do.