We have a 2007 Prius and love it. AND we are now thinking of trading it in for a Subaru Outback. Here in Eastern Washington we get a lot of snow/ice on very hilly terrain. Even with snow tires, you HAVE to get up a head of steam to make it up a hill. If for any reason you are forced to slow down, forget it. The anti-slip control, as many have noted, prohibits acceleration going uphill... any kind of slip and it shuts down. For those who suggest breaking, that doesn't really work if you need to maintain speed up hill.

If there is snow and ice, I immediately put on the cables and that generally works... though even with cables on ice slipping problems cause the drive train to flicker on steep hills. The problem we have is that often we need the cables for the side roads (e.g. our house) but the main roads are cleared and dry. The first winter with the Prius I spent days trying to find some way to turn off the anti-slip control to no avail.