If the S2 really does prove itself, then I think there are a number of advantages, not just size and DSLR-likeness. As you mention, leaf and focal plane shutters is a big advantage for people who use flash and also shoot without, outside.
For me, personally, the big attraction is the glass and the (presumed) lack of hassle with the kinds of tolerance problems Joseph Holmes writes about. Take it out of the box, mount a lens, and shoot. Shims, spacers, lens adjustments, focusing screen adjustments, hunting for good copies of various lenses, especially the wides, missing T/S lenses, and all that stuff just doesn't really appeal to me at all, and although one might not have any problems, like Jack, one might, like Tim. There is just no telling in advance.
I also really like the simplistic interface on this camera.