I have always looked for 100% cotton bedding, and have a tendency to run in horror from polyester. This often results in buying more expensive but fewer items. Fine.. Clothes, I like linen, silk, cotton, wools (esp merino and cashmere) and leather for bags and shoes, especially the lining.
BUT my DH is a scientist and is of the opinion that manmade fibres have come a long way and are just as good, if not better than, natural ones.
I have to admit that my fabric snobbery comes from my grandmother who makes all her own, and mine as a child, and my Mum's clothes and bedding, curtains etc, and maybe the fabrics of old weren't as good as they are now, and of course the high street does seem flooded with synthetics these days...
So, what fabrics do you favour? Can synthetics be OK? And what is viscose (googling is giving me very different results!)