Winter in Yellowstone: A Place of Exquisite Beauty | The Capitalist Muse
I visited the park in the winter several years ago and it simply AWESOME. Quiet. Peaceful. Sunny but quite cold. Personally, I think the slowcoaches are over-rated and would recommend a more modern mode of travel....the historic "cool factor" doesn't justify the cost and increased travel time.
Go to YNP in the winter for a new look at life.