Every time I descend into my unheated basement to do laundry, I note the presence of my shiny hybrid bike over in the corner. Partly on the basis of a tumble early in the season, I have generally been of the opinion that winter cycling in Ottawa is simply too treacherous. Even on bright sunny days, cycling through Centretown is a big pain, likely to involve dangerous confrontations with drivers largely unaware of cyclists near them. In the winter, when bike paths go unplowed and unused, such interactions would necessarily be more frequent, as well as more perilous.
That said, there are some who brave the elements and endure as cycle commuters throughout the bitter winter. While I doubt I will ever acquire their level of commitment, I would consider getting studded tyres and other winter gear if it seemed highly likely that I was going to spend more than a few winters in these conditions.