Rosie,
I'm using EcoWeb from First Ray's (same stuff, different name). I am absolutely committed to it. I have about 30 minis in it. It doesn't break down, it's made from recycled pop bottles, etc... For me, the biggest upside is that I don't need to worry about deterioration of the mount, in contrast to tree fern (1-5 years), sticks (2-10 years) or cork (2-10 years). It seems like mounts hold up well for a long time, and then go downhill very quickly, often taking the plants with them. In my own terrarium, I really keep stuff wet, so mounts fall apart rather more quickly than they might in a more "normal" environment.
Growing moss is really sort of its own art. The way I did it was to put some live moss from the forest into a blender with some dry sphagnum and some RO water. I blended it up, and then "swished" the mounts through the slurry. Bits would lodge in the crevices in the webbing. Within a month, I started to see signs of life. Within 3 months, I had good moss growth on all of the mounts.
Moss requires CONSTANT moisture to get going - high humidity and frequent watering. Fortunately, this is what EcoWeb (EpiWeb) requires, also. For me, I use the health of the moss as a partial indicator of how well I'm doing with watering.
I'm also using some small (1"?) cubes of EcoWeb in pots. So far, so good. I've got a Sophronitis, a couple of Masdevallias, and some Lepanthes in small clay pots with the web cubes. They can be compressed a little, so they hold the plants in place really well - just like Osmunda fiber in the olden days... I have moss growing on the tops of the pots, too.
All this aside - I would ONLY go to Epiweb (Ecoweb) if you are committed to daily watering. It's great because overwatering is practically impossible. The downside is that undewatering would be very easy!
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