I ride all winter here in Toronto Canada and one of the best things I did was go single speed (the second was the use of disk brakes). When I used a derailleur system it would freeze up or skip because the cassette would accumulate with snow and ice. The only thing I would have like to done differently was to add at least one tooth on the single speed freewheel to compensate for the slower speed that is inherent when riding through a lot of snow as compared to my other three season single speed.