[Bergil]

I always thought "power according to his stature" meant that the ring took Smeagol's natural abilities at sneaking and hiding (common to all hobbits, frodo, bilbo, and sam included) and magnified them by its power. The one ring would (by this interperetation) do something simillar to a dwarf's craftsmanship, or the "magic" of an elf or powerful man, though the abilities would come with a catch, a tendency toward evil use.

But what would it give a man? Humans are a varied lot, sort of jacks-of-all-trades but masters of none. it would probably follow individual talent, so a good speaker would get something like the voice of Saruman, an athlete would just gain strength, and some sneaky types would even dissapear. That's my best guess.