I tried felting some optim fibre the other day. Not the most pleasant of fibres to work with. It has a tendency to fly up your nose and almost work it's way into your pores. It is also quite staticky. It takes a bit longer to felt but the end product is definitely very soft. I dyed the two pieces with eucalypt and onion skins and the colour response was quite intense. One was a single layer nuno piece and the other 2 layers of fibre alone.