I used to cross-country all the time. Then I had a chance to go downhill skiing. I thought it would be a piece of cake, but the two are so different, that I couldn't get it at all. And the way the boots are affixed to the skis makes it very difficult to do anything except slide down the hills - including walking around and getting up.

XC skis at only attached at the very front of the toes, so the whole assembly is flexible. You can actually kneel with your knees touching the skis. And moving on skis is actually unlike snowshoeing, but similar to skating.