Hallq: I think for many, many people the apparent plausibility of scientific naturalism is a major deterrent to even taking belief in God seriously. Naturalism claims to tie everything together in one ontology and make God unnecessary. Ultimate reality is either ultimately mental, or else the mental is an accidental by-product. Theism, including van Inwagen's theism (and there are actually versions of the AFR which do not require that the mind be non-material, just so long as it is, in the last analysis, intelligently designed), say that the Ultimate Fact that you cannot go behind is mental. The theists have this point right, and the materialistic atheists have it wrong, if my argument is right.
In Lewis's case the argument led to theism not directly but indirectly, because he embraced Absolute Idealism as a "halfway house" before becoming a theist. It isn't a very popular halfway house these days, but I have seen people, like Daniel Hutto of the University of Hertfordshire, who hold this kind of position.
Let's face it, scientific naturalism is the chief rival to theism at the present time. It's evangelists, like Dawkins are influential, and if you go on the Secular Web you will find it is explicitly dedicated to the defense of naturalism. If it is defeated, the naturalists won't automatically turn to theism (maybe we'll have a revival of Absolute Idealism), but theism will gain in epistemic stature if naturalism collapses.