I wonder whether Jeremy has any comments about comparison with prop drives? One of the almost spooky things about the Mirage drive is that it doesn't seem to be unduly hard work. Clearly dolphins/seals etc 'know' a thing or two that we don't (until Hobie got to work).
The Hobie Mirage drive is ingenious, fairly easy to fit to practically any small boat, has the advantage of being pretty immune from weed fouling and is pretty nicely engineered.
Its only drawback is its relatively poor efficiency, it struggles to convert more than about 40 to 45% of the pedallers power into propulsive force. This is a little bit less than a good rower, a fair bit less than a decent kayak paddler and a lot less than a good propeller.
Although efficiency is important, some of the other attributes of the Mirage drive make it a useful unit. The ability to vary the flapper stroke allows it to be used into shallow water, a distinct advantage over the large diameter propeller needed to gain efficiency from a pedal boat system. The way the flappers fold up close to the bottom of the hull to allow beaching is another useful feature.
Overall, it's a system best suited to the lightest possible hull, preferably one with a high L/D ratio and very low wetted area, as such a hull will be best suited to the relatively low thrust at speed (not the meaningless "bollard pull" static thrust in the Hobie hype) that the Mirage drive gives. It's worth noting that the Mirage drive does give a more constant thrust than rowing or paddling, but less constant than a propeller. It also doesn't create a significant pitching moment, so the hull ends can be finer than that needed for a rowing boat of a similar length.
As always with anything to do with boats, the Hobie Mirage is a compromise. It trades propulsive efficiency for ease of use and fitment, but then so do designers of rowing boats and paddled canoes, or even sailing boats, come to that.
Jeremy
PS: I know that I promised photos of my Electric Winsome, but life has intervened (I got retired a few years early) and I'm short of time to finish her until the Spring.