Wow this is exciting! Hope no-one draws a cartoon of an all season tyre.
It's snowed a couple of times, but not heavily, and been a bit icy on and off. The original Potenzas have been OK. We'll see if we get a real wintry spell I suppose.
I've decided I'm still happy to wait until the back ones really need changing, then go for all season and keep them all year round. Changing and storing wheels is such a faff, not to mention the cost of buying a new set of wheels. If all season are better than summer tyres in winter, and not much different to summer tyres in summer (and this is what I'm expecting), then I'll be perfectly happy with that.
One thing that did occur to me is that everyone who tests proper winter tyres tends to do so in Sweden or Northern Canada and the like. I can imagine that they make a big big difference to all season if the temperature is minus 20 or something and you're driving on 100% snow, but I would hazard a guess that in northern a English conditions, the difference is less pronounced.
All in all I get the compromise argument, but I'll settle for 'slightly better than summer tyres' and an easy life.