Honestly I'm tired of seeing that other banner. Both last week and today I've driven to and from work in blizzard conditions with hardpacked snow and ice on the roads, and I was cruising past all those SUVs and Jeeps that were crawling down the road. Just put a decent set of snowtires on the car, and life is great! What does suck are those Goodyears that come stock on the car. I don't know how those tires got the M+S rating.
Prius does well in snowy condition. as long as the uphill isn't steep (i would say 30% and higher. Don't assume that just because you had a great experience others are making things up. There's a speculation that 06 handles that condition better.
30% and higher ...HAH..I would like to see 4x4's do OK on such a grade. (I think your number ought to be lower. Those REALLY steep mountain grades are not much higher than 15%.
15% is nothing. There's a lot of drive ways where i live that have 30% incline. Obviously it gradually gets to 30% (prius doesn't have the clearance)