cold & wet vs. cold & dry
One of the things I have learned is that I wear a heavier fleece layer on my cold & wet rides because I have a "breathable" water proof layer on my top. Even though it has vents front & a cape back vent & full pitzips it still traps sweat and can feel clammy quicker. It bothers me more on my torso than legs. Although I hate to wear rain pants, some days they just can't be avoided. Without them my water proof socks get full of water which is pretty icky. On cold and dry days I can wear a more breathable jacket with a wind front and can get away with a lighter mid layer. I always wear Cool-max as my base layer because I have a lot of it that I got cheap. I have 1 wool cycling jersey that I like for the cold-dry days, but for commuting it tends not to dry enough for the return trip home on cold-wet days. If I give my polarfleece a hard shake in the morning most of the sweat shakes out and it is bone-dry by evening. I only wear wool socks and just routinely bring a dry pair for the ride home. It is not unusual for me to look more heavily dressed in the spring and fall than in the dead of winter.
it's about the extremities
Like several of the others, I cannot make myself go out in wet + cold, but I can deal with cold and even cold + some wind. I stay comfortable if my fingers, ears, and feet are toasty. I use a fleece headband-type thing around my ears, just under the edge of my helmet. For Christmas the DH got me a wonderful pair of shoe covers (from TE, I believe)--full boot shape. They have made a huge difference. Under those, I also have on wool cycling socks over thin ski sock liners. (I hate being cold.) My feet stay pretty toasty. I need a better pair of gloves for 45 F or less days, but usually my hands start out cold and then warm up as I start working hard. You don't need as much on your torso as you might think, as long as you have a good windbreaker on. Sometimes I end up with too much up there, because once I start pedaling, my top stays really warm (usually Smart Wool under layer, long-sleeve jersey, and windbreaker for me). But I deal with heat much better than cold. Next winter season I plan to invest in warmer gloves and a balaclava.