I, for one, love to winter fly fish. If you're dressed for the weather, and the water isn't "hard", the fish are going to cooperate. The crowds are far smaller (ie: non existent!!), so you've got the full run of the river! A couple things to keep in mind, if you're in snow or serious cold ... If you're wearing felt soled boots in the snow, expect to accumulate large amounts of snow on the bottoms of your boots. The tree branch you could walk under in warm weather may just whack you upside the head when you try to go under! And your guides will probably ice over when you strip line back in. Your next cast will probably go only a few inches! Other than that, it's wonderful!!!
Trouts don't live in ugly places.
A friend is not who knows you the longest, but the one who came and never left your side.
Don't look back, we ain't goin' that way.