This is my first RWD that I am driving through a Toronto winter with OEM 18s and for the most part they've been great. Initially during the first light snow fall, I felt the rear end kick out quite a bit, so decided to save driving the M3 when the roads were dry and clear. However, I had to take the car out during the first major snowfall in 2009 and driving on the snow filled freeways that weren't cleared yet was a little scary. I could feel the rear wheels skid here and there and the back would kick out at times, and to see all the trailers drive by at 100km/hr was definitly frightening, because I'm always fearful of spinning out into their path. But with a little time and practice I got a lot more confident. The good thing is this car doesn't do a 180 like some other RWDs in similar situations. The traction control is quite impressive.
Then as I was returning home, I got stuck on a side street close to home. Just could not move forward. Kicked it in reverse, and the car moved incredibly well. I ended up driving in reverse all the way to my house (about 100 meters) and into my driveway as the snow was quite deep on my driveway too. Driving in reverse is almost better than driving my FWD. I did get some strange looks from people passing by though.
Anyways, I'm driving with MDM on, and in deep snow you almost have to drive in reverse. But I try to avoid taking my car out in 5+ cm of snow.