Your right, techincally, God can't be disproven. Neither can the hypothisis that fluffy pink bunnies roam the skies over some planet in the Alpha Centauri system. Can we make an educated guess as to both? Well, I'm going to put my money on no. However, that is too simple an approach to the question as a whole.
First of all, there must be a distinction made between God and god. Upper-case God generally refers to the God of the Jeudeo-Christo-Muslim deity figure. Lower-case god usually refers to the general concept of a higher being, be it mono- or poly-theistic, Christian, or Alpha Centaurian. This is important, because I find there to be far more evidence against God then god.
As far as God goes, the concept is based on a very all-or-nothing principle of the Bible. Either the whole thing is true and you believe it (of course, 'true' is relative as well, as it does not necissarily mean a literal interpretation of the Bible), or any part is false and you are not Christian. This tends to breed a very insular, non-questioning, xenophobic world-view, as any questioning or attack of the core beliefs is taken as a personal attack on the very core of the self. I find it hard to believe that any being that truely loved the human race would put such a devisive set of rules in place.
Small-g god, however, is different. The possibility of a higher being (perhaps a hyper-evoloved state of a human-like or other intelligent creature) is far more within the realm of reasonable possibility then some being that exists outside of time and space. Also, taken in a liberal manner, god can even be applied to things like the Matrix Theory (a theory that says that if we as a race will ever develop giant simulations of entire worlds and galaxies, chances are that we ourselves are a simulation run by an advanced race in some outside existance.) When god is no longer such a concrete structure, it becomes far more robust and likely.
However, the intelligent design argument in support of religion falls flat on its face right out of the gate. If it is so unrealistic to believe that the general 'stuff' of the universe exists infinitely, and that given an extremely long time, complex structures can arise by chance, then the idea that an omnipotent intelligence pre-dated the most basic forms of matter and energy is a leap of faith to say the least. It really becomes a chicken and egg debate. If the universe is too complex to have been random, it must have been created by god. But god is so complex, how could it have preceded basic elements? And on and on it goes...
Personally, I think that religions in general are giant cults, in essance. They are based on a near-absolute lack of, and in many cases outright suppression of facts, free thought, and logic. The Bible might have been an excelent self-help book in its time, but it has gone entirely too far at this point. Lots of people feel they need answers, and religions are an easy way to get them, true or not. As for how 'miracles' can occur, luckily, logic allows for statistical anomalies. Every event lies along a bell curve of chance, and occasionaly, the bottoms of that curve are hit. Alot of the so-called miracles can also be attributed to genetics or human perseverance. Or just dumb luck.