Yeah, that is
seriously dangerous using snow tires up front, but not in the rear... The big problem in winter driving is not
going, it's
stopping. When you try to stop on snow or ice, what will happen is that the front will have more grip than the rear, and the car will spin very easily.
I had Michelin Arctic Alpins on my SE-R (all 4 wheels

) last winter and they really are awesome in the snow. On Christmas day I was crusin around on completely unplowed roads with 6"-8" of snow on them with no problems. They are good in the rain too (although they sound like a jet turbine when wet). In the dry, they are definitely not performance tires. And the rubber coumpound is quite soft, so they wear pretty rapidly in the dry too.
Andrew - who autoXed his Sentra on Arctic Aplins in the snow last January and beat every AWD car but one