Applicable?, racing, of course not; cruising, I don't know, maybe. Could it work with a prop instead of wheels? The physics is certainly interesting and fairly well explained though. Jake? Wouter?
We did go through this at length and it is a bit of a brain teaser. Bottom line; as long as the drag of the vehicle is less than the energy that can be extracted from the moving air, it can exceed wind speed. We do actually do it on catamarans although it's not DDW because we have to keep some angle on our fixed sails to generate efficient lift.
there is a fella that designed a boat that has a big air driven propeller on the back and a prop in the water - he can drive the boat DDW and you might call it "sailing". It was a jonboat looking thing so I'm not sure if he could exceed windspeed - but he could travel in any direction relative to the wind.
