Update - They're great, but not perfect.....
The underwear experiment is a success and they undies now come off the line soft enough to wear straight away. It makes you wonder what exactly is in the washing powder that makes your clothes go so stiff and scratchy!
The towels are better than they used to be but not as soft as the tumble drier. They are getting softer though so maybe I need to keep using the soapnuts for longer to get rid of the old stuff still lurking in the fibres.
The only disappointment is that they have almost no effect on tougher stains like grass, fruit juice, tomatoes etc. This is where a Biological Powder really wins the day. Despite using a stain remover stick and soaking for hours, these stains just won't come out. I have resorted to buying a small tub of 'Vanish' to use on my daughter's 'little accidents'. Still the whole laundry kit is much cheaper and much greener than it was so I'm happy for now with the Soapnuts and I'll be sticking to them from now on.