I'm looking to buy a supra as well and I live in Denver suburbia...
I NEVER drive up to the mountains, always on salted/sanded roads. I used to drive an old Mitsu. Mighty max, RWD, manual, with a rear end light as a feather and leaf springs bouncy as hell... and I made it all right through some snow storms. (Admittedly, I did use sandbags in the bag.)
But you guys are scaring me; from the posts I've read it seems like the supra might go spinning off helplessly the second I undo the parking brake...
Do you guys live in places where it doesn't snow often or just bad drivers? If it really is that incredibly bad, (remember my truck as a comparison) I might have to not buy it, but tell me otherwise!