I think I got enough experience points to go up a level in foul-weather commuting today. I bike commuted last winter too but I was never very comfortable doing it. Granted, I'm in the SF Bay Area so things are a lot milder here than some of ya'll. Today I zipped in through puddles, showers, and some heavier rain, temps about 50F, without any misery. I was geared up like:

SPD sandals, Sealskinz waterproof socks over 2-layer Wrightsocks
REI semi-breathable pants (front neoprene, back spandex) over bike shorts
Normal short-sleeve jersey

I was actually a bit disappointed that it wasn't more wet. But not disappointed enough to, like, move to Seattle or anything.