I've been bike-commuting through the winter for six years now in Minnesota, riding about an hour each way. Here are a few things that help me stay happy.
1. Exact temperature matters. I dress very differently at 35 than at 20 degrees. Above 20 I think in 10 degree bands, once it gets below 20 then every five degrees makes a difference.
2. Warm feet and hands have a lot to do with warm ankles and wrists. Those are the places that blood flows through to get to our fingers and toes. For my ankles, I've taken to wearing smartwool nordic socks that come up over my calf quite a way, then pulling my tights on over the socks to create a double layer. Below 30 I'll usually add rain/wind pants on top of that.
3. Above 30 I ride in my leather Keen bike shoes, adding neoprene toe covers which are the bottoms of old worn out shoe covers that I cut off. (Thanks LBS for that tip!) Sometimes I'll add Showers Pass shoe covers over that, especially if it's damp out. Yes, the shoe covers don't breathe, but for an hour that's not been an issue for me.
4. Below 30 for many years I wore Shimano gore-tex 'winter' shoes which had little insulation but were somehow quite warm, adding the toe covers and shoe covers as needed.
5. The chemical 'toe warmers' really do work, as do the hand warmers. But it has to get down close to or below zero for me to need those.
6. Last year I picked up a pair of Lake winter shoes at an end-of-season sale... I'd heard they were magical and that's been my experience with them. Last week I rode in 5 degrees with just my medium-weight nordic socks and the Lake shoes and was fine for an hour. With both fingers and toes, I find it's really important to do a lot of wiggling around to keep the blood flowing. Because I could only find road style shoes in my size I bought them, but they are not easy to walk in so if buying full price for touring/commuting I'd go with the mountain style shoe.
7. Although it's not about warm feet, staying upright is a big part of a happy, safe, bicycling experience, and if you live in a part of the country that has ice/snow, consider the nokian studded tires. They understand winter riding in Finland!
Riding in the winter seems crazy until you try it... and the best way to do that is to keep riding through the fall to gradually acclimate and adjust your gear. But having an owl 10 feet in front of me, silently pacing me in my headlight beam through a soft falling snow in the pre-dawn darkness is worth having to wiggle my toes.
I think of bike commuting as the tour that never ends. Happy riding in all seasons!