I suppose the question is, how much does letting the lactic acid sit in the muscle during the descent really affect you in the long run? I mean, even coasting down a hill, you're going to be using your muscles again shortly anyway. Anyway, I certainly don't know the answer, I'm just surprised that riding hills on a fixed gear could be that much easier, especially since coasting is also providing you a rest.

You story is interesting but obviously you're in better shape than those road cyclists you're speaking of, or perhaps they're mashing up the hill on too high of a gear and slowing themselves down. There is so much going on besides just geared vs. fixed- too much to be able to draw a specific conclusion from.