In reply to malc:
They were reccomended to me when I had problems with my knees about 10 years ago. Have used them in my climbing boots ever since.
However, their effectiveness (in my mind) has been questioned by the new 'theory' surrounding bare-foot-running. The thought that no support is better than some support (as it's more natural for the foot) is contrary to the super-feet blurb.
Basically, that was a very convoluted way of saying, if I had problems with my knees now I wouldn't go for super-feet, but 10 years ago they seemed to help so I just keep them in my walking boots out of habit.
I should add that I don't wear my walking boots every day.
Probably not the definitive response you wanted!?