Follow up: bought Blizzak WS70s (studless ice and snow) and had them mounted today on the M3. Drove 40 miles through a winter storm and the car never broke traction. I didn't try to push it to the limits. It also climbed a couple of hills without any issue. Performance on the ice remains to be seen but so far so good.
Glad to see you made the jump to driving year-round with the M3. I am currently NSX-less myself (though my Brooklands Green/Tan '94 is on it's way) so I can't even say I've driven an NSX in the snow (though in high school I got around okay in a 1st-gen RX7 w/o LSD or traction-control for many years in Spokane, which averages 60 inches snow/annually).
For what it's worth, I have had 2x BMW 335I X-drive coupes : sold those but kept my mounted snow tires (studless : I don't believe in studs as you would not believe how horrible Spokane's roads are from the studs...). I have a Z4 convertible (hard-top) w/300hp & 50/50 weight distribution & no ground clearance w/a nice traction control system. I slapped my snows on it & have driven confidently in several snowfalls & ice storms this winter. My daily driver is a wonderful AWD FX50S (mutant-SUV built on G35 platform) that has traction & stability control: it is a TANK (better than my 4wd Tundra w/aggressive M&S tires). So alot of it has to do with the snow tire choice itself & presence of the stability/traction/LSD systems. BMW used to be HORRIBLE in the snow but have come a long way.
That is a beautiful M3 by the way. I just hope the paint doesn't take too much of a beating from the rocks tossed at it (they use a lot of sand/gravel on roads here & then don't sweep it up for 4 months...)
Take care