(ooh, I get a kick out of answering as "a seasoned runner"
)
I'm not that experienced a runner but the running I've been doing has often been in winter around those temperatures. And my experience is that I overheat very easily, and need to take care of hands and head and face long before I need an extra layer on my torso. I'll often wear a biking vest or thin wind jacket on my way there (I take the metro, then run the last part of my route to work, about 45 mins) and may start running with it on but have to peel it off very fast. I run with a hipbelt, and stuff it in there.
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett