I realize this was directed at UR, but I believe I can answer. (At least for myself.)
My (non)belief is based entirely on facts that I've read in books and discovered online. The way I see it is like this (imagine it as a timeline):
1) Positive energy existed. (This is the only 'gap' in my argument, but I'll get to that.)
2) Enough of said energy accumulated in a very small amount of space, causing this energy to be extremely condensed, and yeah, Big Bang. Protons, neutrons, quarks, etc. went flying everywhere, and different sorts were attracted to each other through gravity, eventually creating the elements.
3) Elements, mainly hydrogen and carbon formed a sun, which was at least ten times bigger than the sun we orbit.
4) Eventually this sun "died", exploding into a supernova, and formed a new sun and the planets. (This has happened at least 1023 times independently, so, by pure probability, a planet in the "Goldilocks Zone" like Earth was bound to form.)
5) First you get very basic single-celled organisms, the kind that reproduce a-sexually, eventually you get less basic lifeforms, then somewhat complicated ones, and viola, eventually we have us awesome and complex humans.
Okay, so all of that fits, assuming we can figure out how the initial energy came about. Honestly, I don't know. I do know that all the energy in the universe cancels out exactly to 0, so however it did happen obeys the laws of the universe, because it was really neither created or destroyed. But I don't need to know where that energy came from to abandon my belief in god. After all, the Bible, which should never have had to be revised assuming it came from a supreme being that knew past, present, and future, said god created the Earth. I know how the Earth was formed, some god did not do it. It was also claimed that we, the mighty, amazing, and apparently important mankind, we chosen as the favorite among god's creatures and put here. Er, no, sorry. We evolved from apes. I hate to sound depressing here, but we're not important, and there is no profound reason to our being here. It just happened like that, and some people, with good reason, can't/won't accept it. Which is why fun places like heaven and paradise were created, to get past that fear of dying. I love the concept, man I don't want to die, but it's nothing more than some silly story like the ones people tell their kids about Santa Claus and the Easter Bunny.
But yeah, back to the gap. God really is a "God of the Gaps", as Victor Stenger put it. The more science advances, the smaller the gaps become, and the less places God has to retreat to. An example of this was during the pre-heliocentric times, when the earth was still flat and heaven was just above the clouds. ... Do you see the problem here? We will eventually get to the point where we do know everything (..some day), and even if god did exist (he doesn't) we would have no need for him. Because life as we know it could have (and probably has on other planets) arisen naturally whether a god was there to kick things off or not.
Oh, one more thing. This is directed at any theist. Why is it that none of you have been able to come up with any valid point justifying the existence of god?