I ran Michelin Pilot all seasons on my e46 330 all 12 mos of the year and they got me thru the winter but there were times in snow that I slid around a decent amount.
I currently run Dunlop Winter Sport M3s on my e46 M3 and they are excellent tires. I deal with snow on a regular basis in Chicago. You can safely drive highway speeds in bad conditions with them.
With the hp of the e9x M3, I'd strongly suggest dedicated winter tires.