I live in calgary and this will be my 5th winter of bike commuting. Each winter there's only been about 5 or so days where I would've liked studs, the rest of the time traction is fine. So I haven't really felt the need to buy studs.

However, you don't get Chinooks in Winnipeg to melt the ice, so I suspect you may really appreciate some studs, at least on the front wheel. You might consider getting a cheap spare front wheel and putting studs on it. If conditions look slippery, just switch wheels and off you go.