I agree with TWL. Another point is the claim that these devices "truely stop all resonence sound from your equipment, which actually is suspended on air."
Yes, they are suspended in air with no mechanical connection to the platform. But they are not completely isolated. If you put these feet on a shelf and then a component on the feet and then wiggle the shelf, are they trying to claim that the component won't move? Of course it will move. The shelf will move the magnetic cup, the magnetic field will push against the other part which will push against the component and move it. The movement may be damped but it is not completely isolated.
The other concern is airborne vibrations. Sound waves that strike the component will start it vibrating. These feet can't stop that. I think they will give results similar to spings, air bladders, or soft feet like vibrapods. They make work very well to dampen vibrations but they don't just float your component in air completely isolated from it's surroundings. For that you would need a magic carpet.
