I'd recommend some caution and not getting over-confident.
The quattro system is indeed brilliant at finding traction on snow.
However, the brakes are the same useless pile of ABS vibrating rubbish as any other car when you try to stop again, and because you had the grip and traction to getting going faster, you're gonna need even more time to stop!
Having said all that, as long as you take care with your braking and steering, then for sure, the quattro A8 will get to places other cars can't.
I did take all this account when I bought the M3, but decided in the end that in the 2-3 days a year I might need 4wd I'd either stay at home or hire one
