Trainers are good if you can stand them. For my money skiing is a very good way to spend winter months, primarily because it gets one outside, promotes deep breathing, promotes healthy, positive attitudes, and it's good exercise. When you play in the snow you begin to look forward to the cold months. When others are complaining, you are rarin' to go.

The best skiing for exercise in nordic x-country since it is very aerobic. I like telemark type skiing which is either very good or very bad for the quads, depending on your attitude.