In reply to Trangia:
I found it very hard, even though I am a goodish-intermediate skier (with 30+ years experience) on downhill skis. Telemark skis felt somewhat like cross-country skis with 1960's downhill bindings - i.e., very little control! I made the mistake of doing a two-day backcountry trip in the Canadian Rockies in the depths of winter, with a 20-lb sack on my back, without any practice beforehand on telemark skis. Of course, in really deep powder one can't tell what the skis are really doing, or what one is going wrong. I ended up falling on almost every bend going downhill, and it was a real pain to get up after each fall because the snow was very deep powder - so this required taking off the sack, plunging a ski pole down into the snow up to the shoulder, standing up, getting snow out of goggles, cleaning glasses...).
What I should have done, and would recommend to you, is to practice using telemark skis on groomed downhill pistes for several days until you have the basics down. Telemark skiing is pretty different from both ordinary downhill skiing and cross-country skiing. Trying it out in deep powder in the back-country is not the way to go.
Maybe others have more natural talent on telemark skis! Perhaps your experience with touring skis will stand you in good stead.