Summary: I tried these at CES. They appeared to be designed as a flat response, extremely low distortion headphone for specialized applications, or by some pocket protected engineers who never took the time to listen to them. Maybe they listened to them but have bad taste. Even in speakers you don't want a flat response for enjoyment of commercial product.
Summary: The sound is not the last word in electrostatics but is probably better than any dynamic system,(which should probably be called magnetic or coil system, since there is nothing inherently dynamic about a magnetic speaker). The portable accessories make this very appealing and useful as a back-up system on trips. However, Stax has also produced a compact portable system which I have not heard.