I can't understand the appeal of limiting myself to a single speed, even less so have it fixed so that I can't coast. But, around here it's pretty hilly. No one gear will ever be good enough for everything, and going down hills around here fixed just sounds like torture, to me at least. I'll stick to my gears. I've found I need my granny gear sometimes when I'm commuting with my books on the back.
On the other hand, my grandfather lived down in the flats in Louisiana and he refused to ride anything but a single speed because he just didn't need the added complication. I can respect that, and I even imagine a fixed gear wouldn't be unpleasant in such a flat environment.
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