Hi Carol!
I have not used coir, but use coconut husk chips as potting medium, I add pertlite and/or pumice, and charcoal - don't know if the additions are necessary.
I only started using it a few months ago but so far I have been quite happy with it. It appears to act like little sponges - very light and airy - and if you have recently watered you can actually squeeze the chips and feel water come out of them.
I have heard you need to be careful about watering in coir but seems the chips drain quite well - they do hold moisture well so plants may need less frequent watering than in bark.
Also - I have read that cocohusk breaks down slower than bark so don't need to repot as often. I think I read it should be replace about every 3 years.
The downside, imo, is the lightness of the chips - they fly right out of the pot when dry and float out when watering. And the gnats seem to like the moisture retentiveness as well.
My solution to these issues is to top dress the pots with fir bark chips - holds the cocohusk chips in the pots and seems to keep the gnats at bay a bit.
All in all I like the cocohusk chips and the plants seem to as well!
from me for coconut husk chips