JW. I had a ride on the demonstrator into a short strip in the Torres Strait. I was impressed! The Walter engines are good and very cheap to overhaul - I think they have an engine exchange program, around US$60,000 at 3,000 hours. (Walter is tied in with, or owned by Pratt & Whitney.)
Very spacious aircraft, relatively quiet and comfortable and compared to other STOL aircraft, relatively quick.
Payload could be a little better - it is a heavy aircraft. The fabric control surfaces (rudder and elevators) are "quaint" but obviously work. Very strong undercarriage with massive unusual outboard brakes.
No optional extras - the LET 420 comes with everything!