Surprisingly good - in fact I struggle to notice any wear difference to summer tyres. Don't do many miles though... BUT they are clearly not as grippy as summer tyres when the weather is warmer.
Still delaying judgement though as there is admittedly a chance I've knackered their cold weather performance through temperature cycling, but never heard of this being a problem.
Btw, they're great as well when it comes to generally crappy wet weather too as the water clearing capabilities are really quite astonishing.
Will probably change them in spring but this year's weather and various other things taking my time meant they stayed on until the point where I thought, sod it, might as well leave them now.
In the snow, when it comes to hills or stopping, they make my RWD car more confidence inspiring that Mrs Coyote's 4x4 on standard tyres... even hill starts on snow dispatched with ease.
Don't overtake 5mph crawlers though, they don't like it at all. Must be dangerous to go faster than they are...
Must stop now: sounding like winter tyre fanboy.