Oh winter tires are definitely better, no doubt about that, but what I'm saying is you can get away without them if you know what you're doing. Idealy, its best to get some though. If you only have all seasons or summer tires you need to give much more room to stop, and accelerating needs to be done smoother or you just spin out. Problem is if someone in front of you with good tires decides to do a dead stop, you might not be able to stop on time. I've seen idiots do that too, for no reason at all they'll just dead stop right in the middle of the road when it's slippery.
Even with winters you can spin or slide if not careful. With the -30's it tends not to snow very much and the snow that is on the road just gets packed down to a point where it's almost as slippery and smooth as ice.