Totally understand the question.

Changing URL's is swatting a fly with a frying pan, at best. Even if hyphens made a difference, it's minuscule compared to numerous other variables in determining what could make a site or page rank better...

And as it goes with SE's (mainly google), algorithms change. So what may be a small advantage today could be a small disadvantage next week. (or, a bigger problem)

One never knows, but one can be sure of the inherent risk involved in putting forth the time and effort. I see it as spending $20 on a lotto ticket where the grand prize is $25, and the odds of winning are 1:1000, without knowing what will be the case with search algo's tomorrow. (Not to mention hyphenated domains are hard to promote offline)

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