So besides my personal bias towards winter, there's a lot of good reasons to fish during the winter time, not to mention that if you "hate crowds" you can almost be sure to not find any other anglers on a weekday in January... The Winter is a time when fish are stacked up and once you find one or two, there's usually another two or twenty waiting for you to feed them whatever your fly du jour happens to be. Fly selection is another bonus of winter fishing as you don't have to carry around 12 boxes with complicated representations of all of the different stages of several different insects that might happen to be hatching like you would during the summer. Nope, in the winter time you can go with a few standbys and a couple of the flies that draw the ire of nearly every "purist" angler out there - the good 'ol Worm and Eggs.
Another big plus of winter fishing is the time period for fishing during the winter is very gentlemanly - starts no earlier than 10 o'clock and ends before happy hour is over, perfect. So with a short window of time to fish, you don't have to rummage through 30 different fly patterns, at least not if you want to spend time fishing instead of practicing knot tying. As you might know from having tuned in from time to time to my ramblings, I'm no purist, no one would ever describe me as such. But what I am is a pragmatist. So I cycle between 4 or 5 different patterns, and if those aren't working, well then I'm just not going to catch fish I suppose. In all honesty if you simply have some midges (assorted colors to match your favorite body of water), some small pink soft hackles, some eggs, some worms, and maybe a favorite nymph or two like a pheasant tail or a prince nymph, then you've pretty much got your winter fishing covered in 99% of situations and places.
During the winter months your odds of going out and catching a few fish in the short time span the fishing conditions are conducive are pretty darn good if you follow a few rules.
First rule is this: dress warm, if you don't you won't enjoy the experience regardless of whether the fishing is any good...
Second rule is pick your days and by that I mean don't head to the river if you've got a winter storm warning or 30MPH winds, that will ruin a winter fishing day quick.
Third rule is that you should always size up your tippet in the winter, you'll lose less flies and the fish don't care as they aren't getting pressured very often, I personally fish 2X and 3X Fluorocarbon all winter long, occasionally throwing on 4X if they get picky.
Fourth rule is change your indicator position, leader length and weight at least 20 times before you change flies in any given run or pool etc, trust me this will increase the amount of fish you catch.
Fifth rule is once you find one fish in a good deep slow spot, don't move on quickly, keep fishing it because there's more in there and they aren't spooky in the winter months.
Finally, when you're fishing during the winter, take the time to really read the water and scope out potential places to fish during the summertime like nice deep runs and holding habitat. During the wintertime flows are at some of their lowest points of the year and really do reveal themselves to the attentive fisherman.
So really, what's not to like about winter fishing?