Just put a full length set of Fenders (
http://www.mec.ca/AST/ShopMEC/Cycling/Fenders/PRD~5024-720/planet-bike-cascadia-ii-atb-fenders.jsp) on my trusty mountain bike last night and went for a ride. It was only a few degrees below freezing, but it was snowing and the roads were wet. First impressions:
Madre de dios . . . my feet are dry! I'm not constantly trying to avoid the wet patches on the road any more! After 30 minutes on the snowy roads, my bike is not covered in slush, salt, and grime than needs to be brushed off! I'm actually looking forward to my wet winter ride.
To this point I've been making do with a bit of cardboard over the front and rear racks to keep some of the spray off my butt and face. You cannot be told how awesome biking with real fenders is . . . you must experience it for yourself.
If you don't have them on your bike, put them on!