I rode the Schwalbe Snow Studs (from MEC) on my cyclocross bike here in Calgary last winter. They were quite secure on glare ice and packed snow, as long as I didn't do any crazy stuff. They were, however, significantly less secure on deep icy ruts. I get these on a couple of spots on my commute as during the winter we're always getting freezing and thawing. The Schwalbe Ice Spiker front tire on my mountain bike was definitely superior.

I tended to run my Snow Studs at the higher recommended inflation pressures as often most of my commute was on bare pavement.

Summary - recommended tires, but not the ultimate.