In the winter it is really nice - better views, since some of the hardwood trees along the tracks can actually block the view in the summer due to their leaves - there are no leaves in the winter. Plus - if at all possible, try to travel near a full moon, and get a private room. Then you can turn out the lights in the cabin - once it is dark, (say 6 PM or 7 PM) and enjoy seeing the snow covered landscape with the help of the full moon. Add a distant, occasional whistle of the locomotive, and the changing colored lights of the trackside train signals... If you sit just right you can often see the signals change from green to red as the engine passes the signals.
Also fewer people on the train (less crowded) and lower fares. I really like winter travel - but please don't tell anyone. Lets keep it that way.