I have been smashing this car through the snow the past month!
Traction is insane: this car is an absolutely beast in the snow!
Granted, I have snow tires and with the amount of winter driving I do, I wouldn't drive without them, but the AWD is the best by far off any AWD car I've owned (this is my 4th and two of the previous ones we're Audis).
Weight seems to not be a big deal so far in ice as well, which was my major concern.
Another friend with an E-tron was pretty impressed with the stock all seasons performance in the snow, but personally, I think if you're going to drive in the snow more than one or two days a year, snow tires are totally worth it. This isn't exactly a cheap car and it would suck to crash it...
Check some of the other E-tron forums: there's quite a bit of discussion on how impressively good this car is in the snow.
Good luck!