Excellent thread, just what I really enjoy.
I would quibble with the interpretation raised in the original posting that this song symbolizes the overseer's inhumanity to the common worker. This song, at least the versions I grew up with, all seemed to indicate that the boss wanted to automate something that the worker thought he could do better, so he tried, won, and died - a Pyrrhic (sp?) victory. But it was always the common worker's choice - not imposed from above. In fact, the overseer could quite properly have prevented John Henry from even attempting the contest - but he didn't.
Also, since I had so many different versions, even some with different names (Henry Clay is one) - I always figured this was one of those based-on-a-true-incident-that-grew-larger-than-life-in-the-telling. I figured there really was some poor soul who tried to outdo a steam drill back when they were first being invented; whether he won or not, died or not, or was named John Henry or not, I wouldn't even hazard a guess.