Some people who do use winter tyres rave about them but I've never used them on any of my cars so can't really comment on there effectiveness although from what I understand the different rubber compound & tyre tread cut do make a significant difference over "summer tyres" when driving in cold/icy/snowy conditions. eg; stopping distances reduced/grip levels increased etc.
Also I do hear good things about those "snow socks" as a last resort if you get stuck in snow or have trouble getting traction from your tyres on ice so for £30-£50 there probably a wise investment for us RWD owners just to keep in the car for winter.
http://www.350z-uk.c..._ winter tires
If I had more cash though I'd definitely have a spare set of alloys set up with winter tyres for the Zed in winter.