I'm on the other side of the coin from bikebuddah.

After freezing through my first winter in "normal" clothes, cycling-specific winter wear was a profound revelation. There are two pieces of cool/cold/foul/winter wear I would not do without.

First is cycling specific jacket. They are tailored to fit when you're in a riding position. They have gorilla-length arms, the collars are higher, the front shorter and the back longer. Next, they're vented. Pit-zips are a wonderful thing. With the velcros, I can also brace the wrists open for cooling airflow. And of course, they come in hi-vis with reflective bits. I'm in my fourth year with an Endura Gridlock commuter jacket. (Mens, Womens) Especially when purchased online, it's considerably less expensive than most cycling jackets, and I've found it plenty durable (I've also fallen in it twice).

Second is tights. I have a 'tween seasons pair (Endura Thermolite Pro) and a winter pair (Pearl Izumi AmFib). First, only buy tights that are wind-front or wind resistant. Others simply filter the breeze on the way through. I like tights because they don't bunch behind the knee or in the crotch. They don't bind in front of the knee or at the hip. They don't flap in the wind and they don't get caught on anything. They keep me warm and dry too.

I prefer unpadded tights, wearing cycling shorts underneath. This saves me from having to wash them daily. I also prefer bib tights so that I don't have a second elastic waistband squeezing my middle.

Gloves, shoes and headwear I think there's less of a need for cycling-specific (however the cycling-specific stuff is nice to have, IMHO). But I won't give up my jacket or tights.