Great shirt for the winterA shirt for me is simple, it has to fit well/look good, be durable, and be soft.
This Patagonia flannel hits all the requirements. My wife jokes around that it is my city to mountain shirt, because it is so at home in both places. This flannel is definitely something I only wear in colder weather. It is thick and warm. In the spring or fall, it is perfect because I can wear it by itself (I run hot), so no need to bring a jacket with. In the winter, I just need a light jacket over it, if I am not outside too long.
The flannel does seem to run small though, so keep that in mind when buying it online. I've had 2 versions of this shirt, and I will keep them both for a long time.
They are definitely durable, so they are perfect to buy used when you see them on Patagonia's used gear website.