I'm on my third winter on a set of Nokian W+ tyres (on steelies which do nothing for the looks but the car is filthy from Nov to April anyway) - been superb, £54 a corner and they've saved 15000 miles of wear on my £140 a corner summer tyres so far, not to mention kept my alloys looking great.
Two days after i collected my current car when new, I found myself in 2" of snow, going nowhere - it took that long to make progress up a slight incline that the traction control system actually gave up after 20 minutes.
I've driven on winter tyres in 12" of fresh snow, compacted snow and ice and never had an issue. Biggest problems with winter tyres are..
1. don't get too cocky - the laws of physics only allow so much
2. other road users think they can do the same as you on their wide summer tyres - i've had numerous occassions where cars following me have piroetted into kerbs and barriers because they think they can do what the car in front does
3. it upsets the Range Rover Sport owners that you make progress when they can budge - some might say this is a bonus
