I'm not coming at this from quite the same perspective as chompy, but I do have to agree on one point: it's damned difficult to build a story around human omnipotence (or even not-quite-omni-potence.) That's why probably two thirds of the story branches here wind up with the stone being taken away almost immediately (and most of the rest concern themselves with the way someone's attempts to use its power to fix the problems they caused with its power only screw things up further.) It's why Superman is so difficult to write for. As chompy points out, what's to stop Lucas from simply exploiting portals and her space on the Moon to solve any of the problems driving any of the plotlines? Ethics, in some cases, but there's at least one situation (the invasion of outside forces of darkness) where ethics would lead her towards doing so, not away from.
(I do have to apologize; I should've raised this point when the omnipotence-zone thing was first being discussed, but I really didn't anticipate the portals business...)
