But just between my home and work (1.1 miles each way). Do to my work I sometime do the trip 2-3 times a day (and other times none) but I have been biking all winter long. I live in Johnstown Pa and use studded tires and fenders.
Now in previous Winters I have biked on longer trips, but those were winters where I could use slicks do to lack of snow and ice on the ground (and in my area that can occur as the temperatures reaches into the 20s). Once I switch to studded tires I stop making long trips, the increase resistance of the tires over slicks are enough for me to reduce my biking (Through once spring hits and I switch back I notice that I am still in decent shape for long trips with slicks).
As to overdressing, I rarely do that, first my trips are short (10-15 minutes) but second given the trips are short I am willing to run a little "Cold" when I start knowing I can be in a warm place within 15 minutes. I found out that once I start biking and the body heats up I am no longer cold provided I have adequate protection from the wind (which in my experience a bigger factor in biking than snow, ice and temperature).
What I normally wear are poly-Cotton Army BDUs (When temperatures drop below freezing or if it is raining or snowing I put on a Gore-Tex rain pants) over my legs. I wear my regular tennis shows (So if it rain I can slip over my Neos over-boots). I wear a shirt and a wind proof jacket (and when temperatures below 40 a inner goose down inner-jacket). When It Rains I wear Gore-Tex Jacket (But I tend to take it off when it is NOT raining for it retains to much sweat when I am biking unless I have a lot of clothing underneath it to absorb the sweat). I wear a rain proof hat with a flap that goes under my Neck (And fits beneath my Helmet) and Gore-Tex Gloves (Which I tend to take off if the temperature gets above 40, and add with a glove liner if temperature gets below 25).
I rarely wear long underwear (I do if temperature drops below 20, but that is rare in my area), the poly-Cotton BDU is warm enough when I am biking at temperatures about freezing.
Now when I did do long trips in winter I always changed my T-Shirt half way through the trip. Changing that T-Shirt (Even in 20 degree temperatures) tended to warm my up getting all that Sweat away from the middle of my Back.
Thus biking in Winter is possible, but you have to work around the Temperature and wind (which includes the "wind" you cause by biking at fast speeds).
Picture of My bike (with Trailer). Since I took this picture I removed the top bag at the rear of the bike, it did not have a very secure way to attach to the rear rack, and once I removed the bag I could drop my trailer hitch lower. I rarely use the trailer in winter, but in summer it gives my a lot of space to haul things in. You only notice the trailer going up hill (you have to down shift sooner do to the weight in the trailer) but on the flats no significant difference that I can tell (On my 20 mile trips I use to take I always hauled the trailer behind me).