I grow 99.99% of my orchids in 100% hydroton and regular plastic pots. All of them are doing wonderfully.
I use small grade hydroton for the seedlings as well. I use air cone pots for the big boys and my rupicolous laelias are in fine grade hydroton with regular 3 inch plastic pots. I came upon this method by accident, but I'm VERY pleased with the results. None of my orchids have root problems--in fact, I was watering them yesterday and was actually awed by how healthy the roots are. Some are so extensive they are now peeking outside the bottom of the pots.
The only exception to this are: 1) the miniatures that are in my office--they need more moisutre and the ERIN pots are tiny, so I use moss, 2) my Eulophiella elizabethae seedlings, 3) my 3 phalaenopsis and 4) my alamanea punicea. These are all in plastic pots with moss.
I live in Miami, btw, and grow my plants outside.