back on topic...(I also cross posted this on subaruoutback.org)
Well I guess I'll post here since I have now had this happen to me twice (at least twice it was very noticeable)
My first experience was going on a straight flat road, which was ice covered and it was VERY unsettling. The back end would "wiggle" and it was hard to keep it going in a straight line. At that time there was a decent cross wind so I attributed it to that.
My experience today was on the interstate, ice covered, and the same feeling, but not quite as bad (I have since replaced the RE92 tires, but I have gone to an 8" wheel, which I would assume would just make snow driving worse)
Both times it seems I have had a full load, 5 people in the car, ski stuff in the back and 5 skis/snowboards on the top.
I have driven numerous time with only my wife in much worse conditions and I have not had any issues. Granted it's hard to compare conditions, but I do feel more stable with 2 people and 2 skis, rather than a full load.
Either way, it's not a fun feeling and all I can seem to do is slow way down and let people pass. I'd love to have an explanation, cause it sucks.