It turns out my driveway was a bit of an extreme test - fresh snow between 5 & 6 inches deep, with some slush and crap underneath.
Went out this afternoon and did quite a lot of miles, some of them on quite steep roads. Once clear of nasty driveways, the Sottzeros really do work well - I could pretty much get through anything and I saw 10 cars that struggled more than me for every one that did as well or better. Even the FWD cars were spinning their wheels all over the place.
So I withdraw the bad mood comment this morning - in fact I'm glad I spent the money.