I've done a bit of snow driving so far and the Q4 system handles it well. Initially you feel like you're in a RWD car because of the rear torque bias, which results in very nice positive grip feedback and not a small amount of fun at the same time, but just about the time you feel the rear end is getting loose enough that you need to provide steering input to correct the AWD system remaps the power and starts pulling from the front to balance the power and grip out.
The net result is a car that's rather enjoyable to drive in the snow, lets you play a little and have fun with the conditions, yet still retains plenty of control and grip when you need it. I have the 20" wheels on all seasons and had no problems getting around in the blizzard about a week ago. It's not quite as good as my Range Rover was in the snow, but it's pretty close, and that's a high praise. And the Range Rover was no where near as fun to drive in the sun or the snow!