Speaking of the God of the Gaps™, I was myself accused of believing it just the other day. I was at dinner with Raphael Bousso, Eva Silverstein, Ori Ganor, and some other physicists, and they were discussing fine-tuning and questions involving the precise way in the Multiverse is supposed to explain it.
Well, eventually I got tired of remaining in the closet, and I asserted: "Given that I believe in God for other reasons, I think it's most likely that God chose the Laws of Nature to be conducive to life". Well, this got everyone pretty worked up (in a friendly way) and Raphael tried to apply that ominous phrase: the God of the Gaps™.
Well, it isn't. In my comment, it was completely manifest that I did not believe in a God whose sole purpose was to fill the fine-tuning "gap". I believe in God primarily for other (good, evidence-driven) reasons. Once you already believe in God, it is seems totally natural (supernatural?) that he should pick laws of Nature which support life. Theism isn't an ad hoc hypothesis invented solely to fix the problem of fine-tuning. Whereas the Multiverse is, so I guess I should have made a counter-accusation regarding the Multiverse-of-the-Gaps!
Or perhaps it should be called Naturalism-of-the-Gaps, that touching faith that Naturalism can explain away the apparent meaning and purpose of the Universe (something which is perfectly obvious to many ordinary people, who haven't been trained out of this intuition by a Naturalist worldview masquerading as "Science").
Of course, for all I know God did create gazillions of other universes besides ours, and this is the explanation for the fine-tuning of our universe. But I'm certainly not required to believe that the laws of physics are ultimately due to blind processes which don't care about us. Without that premise, a fine-tuned universe just doesn't seem like as big of a problem. Hence there is no need to fill the gap with elaborate new physics.
(But don't worry, if I think of a wonderful physical explanation with experimental consequences, I'll still be perfectly happy to publish it and collect my Nobel prize... just because I am open to supernatural explanations, does not mean my mind is closed to natural ones.)
The other thing the dinner conversation made clear is that some physicists get seriously nervous about the fact that God can't be described by equations, and is therefore (in their eyes) ill-defined. I'll have something to say about this later, in response to Sean Carroll's debate comments. For now I'll just say that it seemed rather insular to me—there are only a small number of people who are capable of using equations to describe the world, yet everybody else manages somehow. As they say, if all you have is a hammer, everything starts to look like a nail. It is our job as physicists to describe the world as completely as we can using equations, but it does not follow that there are no other ways of gaining knowledge about the world.
Perhaps I should have asked whether any of them had ever had a mystical experience.
On the other hand, somebody else (I think it was Ori) pointed out that Monotheism is the ultimate example of a unification hypothesis—explaining diverse things in Nature based on the operation of a single principle. The elegance of Monotheism seemed to have some appeal to him.
It's a funny thing. These days, the Multiverse is taken seriously by theoretical physicists, yet God isn't. (Although the more old-fashioned types attack both concepts as equally unscientific.) And yet, there is at least some observational evidence for the existence of God (in the way of claimed miracles and visions and so on). On the other hand, there is no observational evidence for the existence of the Multiverse.
Apart from fine-tuning itself, the best that can be said about the Multiverse is that certain types of speculative new physics (such as string theory) might also predict multiple universes with different laws of physics (depending on certain other factors). But it's not like there's any actual experimental evidence for other universes, or for any specific theory which predicts them. It's almost as if people care more about whether an idea has the flavor of Science (or science-fiction) than if there is any actual evidence for it. The most important aspect of Science is always observational support!
(It's important for people like me who study quantum gravity to remind ourselves of this point from time to time. It's always especially ironic when people in my field dismiss concepts for lack of observational evidence, since there isn't much in the way of quantum gravity experiments. meters is just way too tiny to see!)