I've commuted by bike for five or six years, and the main thing that seems to boggle people is that I ride through the Michigan winter. It's <i>a lot</i> easier to handle a fixed-gear mountain bike on ice than a car, though - if the rear tire starts to lose traction, the pedals jump due to the decrease in rolling resistance, and my legs reflexively stabilize them.<p>Fifteen miles with snow is probably pushing it, though - I've only done up to six in the winter.