I've been fishing the CDC and Elk for about 10 years now, and its caught fish for me through out the Northeast and on the Grand and Upper Credit Rivers in Ontario. In any given year it accounts for over half the trout I catch and is pretty much the only caddis dry I carry in my box. Now I disagree with Padric about it being a flat water fly. I fish it in fast water/riffle water, and I'll skitter it as it crosses the current at the end of a drift. One reason might be is that mine is not tied as sparse as Hans ties his. Even if it does sink, it's not a bad subsurface pattern. At the end of most drifts, if it sinks I'll strip it back to me.
Hans can afford to be fussy about what type of CDC he uses to tie the pattern. I get the impression that the quality of CDC available in Europe is a lot better than what we see over here. I use whatever feather I pull out of the bag as long as it matches the size that I'm tying.
I'll treat the deer hair with WaterShed on some CDC and Elks and, to be honest, where I wasn't careful enough, and it got into the CDC once it dried it didn't seem to have any impact on the CDC.
If you haven't tried it, give it a try, it's a quick easy tie and very effective. With the colors of CDC now available you can match just about any caddis hatch you'll run into around here. The only one I can't match with it is the Little Black Caddis. I use a CDC and CDC to match that one.