Kev, there are alot of folks who own Zs here in the Northern VA and Maryland area so I suspect you'll get some feedback once they see your post. My Z isn't a daily driver so in the winter its out only when the roads are clear and dry. That said, as AK370 has posted above there are folks who live even farther north who do drive in the winter with the right set of tires. Also, stop by on any Saturday morning at the Starbucks in Fairfax by Kohls starting at 10AM and meet up with us 370Z owners who get together each weekend. You can get answers there as well to your questions.
NOVA: Zs & Coffee - Starbucks every Saturday @ 10AM