I currently live in the Northest corner of CT and i have a 03 330Ci 5sp manual and for the winter i run a set of bizzak snow with all 4 tires studded and i have had zero issues with getting around in deep or heavy snow. SeanC is right you will regret not having the RWD in the summer months. If you are a good winter time driver and with a set of studded snow tires you will be fine.
BIMMER FOR LIFE!!