This will be my 1st winter as well. I have a 2012 Model S RWD and I'm getting a set of Bridgestone Blizzak's in a few weeks. Yeah, I'm in for a challenge, I have no doubt. One thing to be thinking about is the level of your regenerative breaking. I did "test" the roads out with my summer tires when we had a good snowfall a few weeks ago. Not sure about the settings on the M3 but be sure to set your regenerative braking to low otherwise just letting of the "gas" can cause you to slide.