Hi Barbara -
The man who started the trend is Nic van den Bosch, in Tasmania.
http://www.vision.net.au/%7Enicvdb/index.htm
After browsing his website, I tried a couple of cymbidiums in HM, and found they grew enthusiastically. So, now all of my cymbidiums are potted in fresh horse manure. Only caveat - run water through the pots daily for the first month or so, to flush out salts.
I also use a mix of about half HM for genera like Cycnoches and Catasetums, which thrive in the rich mixture. Again, daily water flush.
With the Cymbidiums, my care has evolved: about twice a year, I lift the entire plant, add another 4" or so under the roots, and drop the plant back into the pot. This replaces the loss of medium from composting/decomposition.
Cymbidiums seem to appreciate being fiarly crowded, but my flowering with this growing method has been pretty spectacular.
I live in the deep south, US, so my Cyms. are strictly outdoor plants. When in bloom, they go into the front yard. If you grow indoors, you may want to rethink the HM, though I do not find that it is at all stinky. Smells like horse.
Regards - Nancy