Things I learned this winter:
Windproof shell over hoodie and other shirt is very comfortable, even with a -30 windchill.
Boots without holes will need to be purchased before next winter, because I know I'm too lazy/forgetful to tape them or put baggies over my feet.
Fenders do not necessarily equal dry and clean upon reaching destination (i.e. do not wear work pants on the bike in the winter).
Smartwool makes an excellent underlayer.
Very light track bike w/skinny tires + 40lbs of groceries on the back = very cautious and annoying ride home. I know to use a bike with some substance now.
Apparently, very, very cold temperatures make it very difficult for drivers to pay attention to anything but themselves.
That's all.
Overall, fantastic and fun winter riding (made it out every single day this year), but very happy to see spring around the corner!