Over the past few winters I've been quite pleased with the Yokohama Geolandar AT/S all terrains on the Superu. This year, we're kicking it up a notch and shoeing up with a set of General Altimax Arctics.
Update: These tires are on and they are quieter than the Yokohama's they replaced. Grip is good in dry and wet conditions and so far, I am very pleased with them. Will report back soon with snow updates.
January update: SNOW!!! These tires bite into snow remarkably well and have been very good on ice. Lots of grip and strong lateral stability.