I'm partial to string theory first, because my son is researching it as a Ph.D. student at the U. of Arizona, and second, because it really does seem the best way we know right now to explain a great deal about our universe. If it's true, the universe is far stranger than we had imagined -- but hasn't that always turned out to be the case? Go back 100 years, 200 years, 500 years, and people always thought they had it all figured out. And they always turned out to be drastically wrong about nature. The latest Scientific American has an article by the (I think Italian) physicist who first proposed string theory in 1968. He was using it to explain actions of subatomic particles, not the whole shebang, and he dropped it after a while. Then, once other scientists had begun to develop string theory, he returned to the field. Anyway, he makes specific predictions that may be possible to prove or disprove soon. -- Joe
Once D-brane theories make testable predictions (and we have the colliders/apparatus to test them), the physical understanding should follow. Quantum mechanics does odd things to your perception of the ordinary world. Fun, but strange.