Now the counterargument to that is you drive to the conditions / don't drive any quicker than you would if you had summer tyres all round, however we all know thats BS, it would be all too tempting even for those with lots of self control to keep building up more speed as your confidence in the front tyres increases.
It's a recipe for disaster imho.
I see those as short term solutions, with winter tyres you could blast down an A road at 50 / 60mph, you can't really do that on snow chains or socks.